Thomas Dorsey was born in Shenandoah, Pennsylvania and is the younger brother of Jimmy Dorsey.

He worked with many bands in the New York City area starting in the 1920s, including the bands of Rudy Vallee, Vincent Lopez, and Paul Whiteman. With brother Jimmy, he led the Dorsey Brothers Orchestra until they split up (with some acrimony) in 1935. The brothers also appeared as session musicians on many jazz recordings.

Tommy Dorsey formed his own band, which was very successful, scoring 137 Billboard chart hits, including his best-known song, I'm Getting Sentimental Over You (which showcases his phenomenal range, reaching up to the high C #). The band featured trumpeters Bunny Berigan and Charlie Shavers, arranger Sy Oliver, and singers Jo Stafford, Dick Haymes and Frank Sinatra. Sinatra achieved his first great success as a vocalist in the Dorsey band and claimed he learned breath control from watching Dorsey play trombone. Dorsey said his trombone style was heavily influenced by that of Jack Teagarden.

Dorsey married Jane New (1924??- August 24, 2003) in 1948 and she remained his wife until his death. She had been a dancer at the world-renowned Copacabana. After Dorsey's death, Jane obtained the rights to her late husband's band and renamed it The Tommy Dorsey Orchestra, a group which continues to play to this day (see]). Jane Dorsey died of natural causes around the age of 79 in 2003.

In 1956, Tommy Dorsey died at age 51 in his Greenwich, Connecticut home in his sleep, choking on food. Dorsey and his wife Jane New are interred together in Kensico Cemetery in Valhalla, New York. Sinatra released a tribute album to Dorsey in 1961 entitled I Remember Tommy with arranger by Sy Oliver.