Breen was raised in Yonkers, New York, and attended St. Paul the Apostle Catholic grammar school.

For the 1997–98 season, Breen was promoted to television play-by-play for the Knicks, as Marv Albert was fired from MSG Network following his infamous sex scandal.

For the 1998 NBA playoffs, Breen joined NBC as a backup play-by-play announcer, and he remained in that role until the end of the network's coverage of the league in 2002.

calls include Stephen Curry's game-winning 38-foot three-point shot vs. Oklahoma City in February 2016, Ray Allen's game-tying shot against San Antonio in the 2013 Finals, and Luka Dončić’s game-winning buzzer-beater in overtime against the Clippers in the 2020 playoffs.

He then decided to test the saying out in the booth when announcing games; he got an immediate positive reaction and stuck with it all throughout his career, making it his trademark.

When the Knicks made the 2011 NBA Playoffs, Breen did not call any of the games for MSG due to his involvement with ESPN and ABC; he did call Games 3 (with the MSG broadcasts handled by Kenny Albert) and 4 for ESPN and ABC, respectively.

While working alongside Bill Walton on ESPN, Breen was on hand for the infamous Pacers–Pistons brawl on November 19, 2004.

Following NBA Live 18, Breen and Van Gundy were replaced by Ed Cohen and Jay Williams.

When presented with the Curt Gowdy Media Award, Breen stated in his acceptance speech, “I’ve had this enormous privilege to call so many great moments in NBA history, but the best part, the best part, has always been the lifetime of friendships that the game has given me.”[11] In Game 7 of the 2022 Eastern Conference Finals, as well as the first two games of the 2022 NBA Finals, Breen sat out of the broadcasting team due to a positive COVID-19 test, and was replaced by Mark Jones.

[13][14] In 2023, following a wave of layoffs which included his partners Jeff Van Gundy and Mark Jackson, Breen was the only remaining commentator in the lead broadcast team, with Doris Burke and former NBA coach Doc Rivers joining the lead team.

Breen served as a play-by-play announcer for NBC Sports coverage of men's and women's Basketball at the 2008 Summer Olympics.

From 1988 to 2000, Breen did the sports segment on the WFAN and nationally syndicated Imus in the Morning talk/comedy radio show.