He is the younger brother of pitcher Jeff Weaver.
He made his MLB debut on Saturday, May 27, 2006, starting against the Baltimore Orioles. He pitched seven shutout innings, striking out five, and earning the victory. This was followed with three more consecutive victories. Despite his success, when Bartolo Colón returned from the disabled list, Weaver was bumped out of the rotation and sent back down to the minors. He was recalled to the majors on June 30, 2006, when the Angels designated his brother, Jeff, for assignment.
After receiving nine wins without a loss at the start of his Major League career, tying the American League record set by Whitey Ford in 1950, Jered recorded his first loss on August 24, 2006 when he lost to the Boston Red Sox, despite allowing only one earned run in seven innings pitched, a home run to David Ortiz. He lost his second consecutive game to the Seattle Mariners on August 26, 2006, in which he gave up back-to-back home runs to begin the first inning and surrendered five earned runs in 4 2/3 innings.
He has an exceptionally straight fastball which he can control very well, as well as a changeup, slider and a curveball. He also throws sidearm occasionally for a strikeout or to fool hitters.
On June 28 2008, he and José Arredondo combined to no-hit the Los Angeles Dodgers over eight innings, but still lost the game 1-0. This was only the fourth time in Major League history that a no-hit bid was unable to go nine innings because of the home team winning the game, and the first as a combined effort. Because they did not pitch nine innings, it is not officially considered a no-hitter.
Weaver made his first career relief appearance at against the Boston Red Sox at Fenway Park in Game 4 of the 2008 ALDS. He recorded the win in the bottom of the 12th inning in order to keep the Angels', who previously were down 2-0 in the series, hopes of winning the series alive.