Koufax's career peaked with a run of six outstanding seasons from to 1966, before arthritis ended his career at age 30. He was named the National League's Most Valuable Player in , and won the 1963, , and 1966 Cy Young Awards by unanimous votes, when there was only one Cy Young award made for all major league pitchers, unlike now when an award is made for each league. In all three seasons, he won the pitcher's triple crown by leading the league in wins, strikeouts, and earned run average (he actually led both leagues in all three categories). A notoriously difficult pitcher for batters to face, he was the first major leaguer to pitch more than three no-hitters (including the first perfect game by a left-hander since 1880), to average fewer than seven hits allowed per nine innings pitched in his career (6.79; batters hit .205 against him), and to strike out more than nine batters (9.28) per nine innings pitched in his career. He also became the 2nd pitcher in baseball history to have two games with 18 or more strikeouts, and the first to have eight games with 15 or more strikeouts.
Among NL pitchers with at least 2,000 innings pitched who have debuted since , he has the highest career winning percentage (.655) and had the lowest career ERA (2.76) until surpassed by Tom Seaver, whose NL career mark is 2.73. His 2,396 career strikeouts ranked 7th in major league history upon his retirement, and trailed only Warren Spahn's total of 2,583 among left-handers. Retiring at the peak of his career, he became, at age 36 and 20 days, the youngest player ever elected to the Baseball Hall of Fame.
Koufax is also known as one of the outstanding Jewish athletes of his era in American professional sports. His decision not to pitch Game 1 of the 1965 World Series because game day fell on Yom Kippur, the Jewish Day of Atonement, garnered national attention as an example of conflict between social pressures and personal beliefs.
Koufax attended Brooklyn's Lafayette High School, where he was better known for basketball than for baseball. When he started high school, school sports were not available because the New York teachers were refusing to supervise extracurricular activities without monetary compensation. As an alternative to school sports, Koufax started playing basketball for a local Jewish Community Center team. After the labor action was settled, he played for the high school basketball team. During his senior year, he became team captain and ranked second in his division in scoring, with 165 points in 10 games.
While attending high school, Koufax also played baseball. In 1951, at the age of 15, Koufax began playing in a local youth baseball league known as the "Ice Cream League". He started out as a left-handed catcher, and the next year moved to first base; he also played first base for the Lafayette High School team. While playing for Lafayette, he was spotted throwing the ball around the infield by Milt Laurie, the father of two of Koufax's teammates and coach of the Coney Island Sports League's Parkviews. Laurie recognized that Koufax might be able to pitch, so he recruited the 17-year old Koufax to pitch for the Parkviews.
Koufax graduated from high school and attended the University of Cincinnati on a basketball scholarship. In spring 1954, he made the college baseball varsity team. That season, Koufax went 3–1 with 51 strikeouts and 30 walks, in 31 innings. Bill Zinser, a scout for the Brooklyn Dodgers, sent the Dodgers front office a glowing report that apparently was filed and forgotten.
After trying out with the New York Giants at the Polo Grounds, Koufax went to the Pittsburgh Pirates at Forbes Field. During the tryout with the Pirates, Koufax's pitching broke the thumb of his catcher, Sam Narron, the team's bullpen coach. Branch Rickey, then general manager of the Pirates, told his scout Clyde Sukeforth that Koufax had the "greatest arm [he had] ever seen". The Pirates, however, failed to offer Koufax a contract until after he was committed to signing with the Dodgers.
Dodgers scout Al Campanis learned about Koufax from a local sporting goods store owner. After seeing Koufax pitch at Lafayette High School, Campanis invited him to a try out at Ebbets Field. Dodgers manager Walter Alston and scouting director Fresco Thompson watched as Campanis assumed the hitter's stance while Koufax started throwing. Campanis later said, "There are two times in my life the hair on my arms has stood up: The first time I saw the ceiling of the Sistine Chapel and the first time I saw Sandy Koufax throw a fastball. The Dodgers signed Koufax on a $6,000 salary with a $14,000 signing bonus. Koufax planned to use the signing bonus as tuition to finish his university education in case his baseball career failed.
Koufax made his major league debut on June 24, , in the fifth inning against the Milwaukee Braves with the Dodgers trailing 7–1. Johnny Logan, the first batter Koufax faced, got a bloop single. He was followed by future Hall of Famers Eddie Mathews and Hank Aaron. Mathews bunted, and Koufax calmly fielded the ball and threw it into center field, trying to get Logan on the force. Aaron then walked on four pitches to load the bases. Bobby Thomson was the next batter, and after working the count full, he struck out swinging. Thomson had just become Koufax's first strikeout victim.
Koufax's first game as starting pitcher was on July 6. He lasted only 4 2/3 innings, giving up eight walks. He did not start again for almost two months, but he made the most of it when it did happen. On August 27, playing at Ebbets Field against the Cincinnati Reds, Koufax threw a two-hit, 7–0 complete game shutout for his first major league win. Koufax made only 12 appearances in 1955, pitching 41.7 innings and walking almost as many men (28) as he struck out (30). His only other win in 1955 was also a shutout.
During the fall, he enrolled in the Columbia University School of General Studies, which offered night classes in architecture. The Dodgers won the 1955 World Series for the first title in franchise history—but without any help from Koufax, who sat on the bench for the entire series. After the final out of the Series, Koufax drove to Columbia to attend class.
1956 wasn't very different from 1955 for Koufax. Despite the blazing speed of his fastball, Koufax continued to struggle with control problems. He saw little work, pitching only 58.7 innings, walking 29 and striking out 30; he had a 4.91 ERA. Rarely was he allowed to work out of a jam. As soon as he threw a couple of balls in a row, Alston would have somebody start warming up in the bullpen. Jackie Robinson, in his final season, clashed with Alston on several different subjects, including Koufax. Robinson saw that Koufax was talented and had flashes of brilliance, and objected to Koufax being benched for weeks at a time.
To prepare for the season, the Dodgers sent Koufax to Puerto Rico to play winter ball. On May 15, the restriction on sending Koufax down to the minors was lifted. Alston gave him a chance to justify his place on the major league roster by giving him the next day's start. Facing the Chicago Cubs at Wrigley Field, Koufax struck out 13 and earned a complete game win. It was his first complete game in almost two years. For the next two weeks, and for the first time in his career, he was in the starting rotation. Despite winning three of his next five, leading the league in strikeouts and having a 2.90 ERA, Koufax didn't get another start for 45 days. In his next start, on July 19, he struck out 11 in seven innings, but got a no decision. On September 29, Koufax became the last man ever to pitch for the Brooklyn Dodgers before their move to Los Angeles, by throwing an inning of relief in the final game of the season.
Over the next three seasons, Koufax was in and out of the Dodger starting rotation due to injuries. He started the 1958 season strong by going 7–3 through July, but ended up spraining his ankle in a collision at first base. He finished the season with an 11–11 record, leading the league in wild pitches. In June 1959, Koufax struck out 16 Philadelphia Phillies to set the record for a night game. On August 31, 1959, he broke that record and tied Bob Feller's major league record for strikeouts in one game with 18 strikeouts, (and broke the modern NL record of 17, by Dizzy Dean in 1933), pitching in Los Angeles against the Giants.
In , the Dodgers won a close pennant race against the Milwaukee Braves and the San Francisco Giants and went on to face the Chicago White Sox in the World Series. The opening game of the series was in Chicago, and Koufax pitched two perfect innings in relief, though they came after the Dodgers were already behind 11–0. Alston gave him the start in the fifth game, played at the Los Angeles Coliseum in front of 92,706 fans. He allowed only one run in seven innings, but was charged with the loss in the 1–0 game when Nellie Fox scored on a double play. However, the Dodgers came back to win the Series in Game 6 in Chicago.
In early , Koufax asked Dodgers GM Buzzie Bavasi to trade him because he wasn't getting enough playing time. By the end of 1960, after going 8–13, Koufax was thinking about quitting baseball to devote himself to an electronics business that he'd invested in. After the last game of the season, he threw his gloves and spikes into the trash. Nobe Kawano, the clubhouse supervisor, retrieved the equipment to return to Koufax the following year (or to somebody else if Koufax did not return to play).
The next day, Koufax was pitching for the "B team" in Orlando. His teammate, Ed Palmquist, missed the flight, so Koufax was told he would need to pitch at least seven innings. In the first inning, Koufax walked the bases loaded on 12 straight pitches. Sherry told him, as he'd been told before, to take something off the ball to get better control. Koufax finally listened and struck out the side. By the time he came out of the game after seven innings, Koufax had struck out eight batters, walked five and given up no hits.
Koufax finally broke into the starting rotation permanently. On September 27, Koufax broke the National League record for strikeouts in a season, surpassing Christy Mathewson's 58-year-old mark of 267, set in . Koufax finished the year 18–13, with 269 strikeouts and 96 walks. During the two All-Star Games, Koufax pitched two innings without giving up a run.
That same season, Koufax's pitching hand was injured. In a batting appearance in April, Koufax had been jammed by a pitch from Earl Francis. Soon a numbness developed in Koufax's index finger on his left hand, and the finger became cold and white. Koufax was pitching better than ever before, however, so he ignored the problem hoping that it would clear up. By July his entire hand was becoming numb and he had to leave some games early. In a start in Cincinnati, his finger split open after one inning. A vascular specialist determined that Koufax had a crushed artery in his palm. Ten days of experimental medicine successfully reopened the artery. Koufax finally was able to pitch again in September, when the team was locked in a tight pennant race with the Giants. Trying to get back into shape after the long layoff, Koufax was ineffective in three appearances as the Giants caught the Dodgers at the end of the regular season, forcing a three-game playoff.
The night before the National League playoffs began, Manager Walter Alston asked Koufax if he could start the first game the next day. With an overworked pitching staff, there was no one else, as Don Drysdale and Johnny Podres had pitched the prior two days. Koufax obliged. Koufax later said, "I had nothing at all." He was knocked out in the second inning, after giving up home runs to Hall of Famer Willie Mays and Jim Davenport. After winning the second game of the series, the Dodgers blew a 4–2 lead in the ninth inning of the deciding third game, losing the pennant.
The Dodgers faced the New York Yankees in the 1963 World Series, where Koufax beat Whitey Ford 5 to 2 in Game 1 and struck out 15 batters, breaking Carl Erskine's record of 14 in the 1953 World Series (Bob Gibson would break Koufax's record by striking out 17 Detroit Tigers in Game 1 of the 1968 World Series). Yogi Berra, after seeing Koufax's Game 1 performance, was quoted as saying, "I can see how he won 25 games. What I don't understand is how he lost five. In Game 4, he completed the Dodgers' series sweep of the Yankees with a 2 to 1 victory over Ford, earning the World Series MVP Award for his performance.
On August 8, Koufax jammed his pitching arm while diving back to second base to beat a pick-off throw. He managed to pitch and win two more games. However, the morning after his 19th win, a shutout in which he struck out 13, he could not straighten his arm. He was diagnosed by Dodgers' team physician Robert Kerlan with traumatic arthritis. Koufax finished the year with an impressive 19–5 record.
Despite the constant pain in his pitching elbow, Koufax pitched 335⅔ innings and led the Dodgers to another pennant. He finished the year by winning his second pitchers' Triple Crown, leading the league in wins (26), ERA (2.04) and strikeouts (382; the second highest modern day total). His strikeout total set a modern (post-1900) record that lasted until , when Nolan Ryan struck out 383 batters. He held batters to 5.79 hits per nine innings, and allowed the fewest base runners per 9 innings in any season ever: 7.83, breaking his own record (set two years earlier) of 7.96. Koufax had 11-game winning streaks in both 1964 and 1965. Koufax captured his second Cy Young Award (again unanimously).
Koufax and the Dodgers faced the Minnesota Twins in the World Series. Koufax declined to pitch Game 1 due to his observance of Yom Kippur; with Drysdale pitching, his team was hit hard. In Game 2, Koufax pitched six innings, giving up two runs, but the Twins won the Game 5–1 and took an early 2–0 lead in the series. The Dodgers fought back, with Claude Osteen, Drysdale, and Koufax claiming vital wins to take a 3-2 lead back to Minnesota. In Game 5, Koufax pitched a complete game shutout, winning 7–0; however, the Twins won Game 6 to force a seventh game. Starting Game 7 on only two days of rest, Koufax pitched through fatigue and arthritic pain, throwing a three-hit shutout to clinch the Series. The performance was enough to win him his second World Series MVP award. Also, in 1965 he won the Hickok Belt a second time, the first (and only) time anyone had won the belt more than once. He was awarded Sports Illustrated magazine's Sportsman of the Year award.
On September 9, 1965, Koufax became the sixth pitcher of the modern era to throw a perfect game. The game was Koufax's fourth no-hitter, setting a Major League record (subsequently broken by Nolan Ryan). Koufax struck out 14 batters, the most recorded in a perfect game. The game also featured a quality performance by the opposing pitcher, Bob Hendley of the Cubs. Hendley pitched a one-hitter and allowed only two batters to reach base. Both pitchers had no-hitters intact until the seventh inning.
In one of baseball's great statistical and score-keeping anomalies, this has been the only nine-inning major league game where both teams combined for one hit. The game's only run, scored by the Dodgers, was unearned. The Dodger run was scored without a recorded at bat—Lou Johnson walked, reached second on a sacrifice bunt, stole third, and scored when the throw to get him out at third went wild.
Koufax and Drysdale didn't report to spring training in February. Instead, they both signed to appear in the movie Warning Shot, starring David Janssen. Drysdale was going to play a TV commentator and Koufax was going to play a detective. Meanwhile, the Dodgers waged a public relations battle against them. After four weeks, Koufax gave Drysdale the go-ahead to negotiate new deals for the both of them. Koufax ended up getting $125,000 and Drysdale $110,000. They rejoined the team in the last week of spring training.
The Dodgers went on to face the Baltimore Orioles in the 1966 World Series. Game 2 marked Koufax's third start in eight days. Koufax pitched well enough—Baltimore first baseman Boog Powell told Koufax's biographer, Jane Leavy, "He might have been hurtin' but he was bringin'"—but three errors by Dodger center fielder Willie Davis in the fifth inning produced three unearned runs. Baltimore's Jim Palmer pitched a four-hitter and the Dodgers ended up losing the game 6–0. Alston lifted Koufax at the end of the sixth inning with the idea of getting him extra rest before pitching a potential fifth Series game. It never happened; the Dodgers were swept in four, not scoring a single run in the last three. After the World Series, Koufax announced his retirement due to his arthritic condition.
Koufax married Anne Widmark, daughter of movie star Richard Widmark, in 1969; the couple was divorced in the 1980s. He then remarried and divorced again in the 1990s.
In his first year of eligibility in , Koufax was elected to the Baseball Hall of Fame, just weeks after his 36th birthday. His election made him the Hall's youngest member ever, five months younger than Lou Gehrig upon his induction in 1939. On June 4 of that same year, Koufax's uniform number 32 was retired alongside those of Dodger greats Roy Campanella (39) and Jackie Robinson (42).
The Dodgers hired Koufax to be a minor league pitching coach in . He resigned in , saying he wasn't earning his keep, but most observers blamed it on his uneasy relationship with manager Tommy Lasorda. In , Koufax discontinued his relationship with the Dodgers when the New York Post (which, like the Dodgers, had become part of Rupert Murdoch's business empire) published a story reporting rumors about his sexual orientation, and implying that Koufax was gay. Koufax returned to the Dodger organization in when the Dodgers were sold to Frank McCourt.
In , The Sporting News placed Koufax at number 26 on its list of "The 100 Greatest Baseball Players. That same year, he was named as one of the 30 players on the Major League Baseball All-Century Team. Although he rarely makes public appearances, he went to Turner Field in Atlanta for the introduction ceremony before Game 2 of the World Series.
In an article in 1976 in Esquire magazine, sportswriter Harry Stein published an "All Time All-Star Argument Starter," consisting of five ethnic baseball teams. Koufax was the left-handed pitcher on Stein's Jewish team.
More than four decades after he retired from baseball, Koufax was the final player chosen in the inaugural Israel Baseball League draft in April 2007. Koufax, 71, was picked by the Modi'in Miracle. "His selection is a tribute to the esteem with which he is held by everyone associated with this league," said Art Shamsky, who managed the Miracle. "It's been 41 years between starts for him. If he's rested and ready to take the mound again, we want him on our team." Koufax declined to join the Miracle, despite the fact he would have been working on 14,875 days rest.
On May 14, 2007, Upper Deck Authenticated signed Koufax to an exclusive autograph and memorabilia agreement.