He was traded to the AFL's Miami Dolphins in 1969. He continued to play well with the Dolphins, in 1969-1974 and 1976, and made the AFL All-Star team in 1969 and the NFL Pro Bowl in 1972 and 1973. Named All-AFC in 1972 as well.
His leadership made him a cornerstone of the Dolphins' defense. During his years there, the team advanced to three consecutive Super Bowl appearances, one of which was the team's 1972 undefeated season. In 1973, he recorded a then-team record 162 tackles (91 unassisted). He was named to the AFC-NFC Pro Bowl in 1972 and 1973.
Buoniconti ended his career with an unofficial 24 sacks, eighteen with the Patriots and six while with the Dolphins.
He was named the Dolphins' Most Valuable Player three times (1969, 1970, 1973). In 1990, he was voted as a linebacker on the Dolphins' Silver Anniversary All-Time team. A year later on November 18, 1991, he was enshrined on the Dolphin Honor Roll at Joe Robbie Stadium.
Buoniconti got his law degree during his years with the Patriots. He was a practicing attorney for a short time. He was also President of the US Tobacco Company during the late 1970s and early 1980s. He was a leading critic of studies which showed that smokeless tobacco caused cancer of the mouth as well as other types of cancer.
In recent years, he has become the most outspoken member of the 1972 Undefeated Season team. It is rumored that he leads a champagne toast every year after the last remaining undefeated team loses for the first time. Also, it is reported that Buoniconti sends a Christmas card every year to former Minnesota Vikings defensive end Bob Lurtsema, whose roughing-the-passer violation in an early 1972 game aided the Dolphins' undefeated season.
Buoniconti also appeared in one of the American Express "Do you know me?" TV ads, in which he talked about the No-Name Defense. The punch line was a variation on an old joke, with Buoniconti remarking that everyone knows him now. A passerby remarks, "Hey, I know you... you're... uh... uh..." trying to recall Buoniconti's name. Upon being told that it's Nick Buoniconti, the passerby says, "No, that's not it."
Buoniconti put his verbal talent to use as a co-host of the HBO series Inside the NFL until 2001. That same year, Buoniconti was named to the Pro Football Hall of Fame.
In 1985, after his son Marc suffered a paralyzing spinal cord injury making a tackle for The Citadel, Nick became the public face of the group that founded the Miami Project to Cure Paralysis, now one of the world's leading neurological research centers.
Buoniconti is a member of the National Italian American Sports Hall of Fame.