Diamond was born and raised in Brooklyn. He spent his early career as a writer in the Brill Building, and had an early success writing the song "I'm A Believer" for The Monkees. He signed a deal with Bang! Records, and had a string of singles as the primary performer, including "Kentucky Woman", "Cherry, Cherry", and "Solitary Man".
In 1973, Diamond hopped labels again, this time to Columbia Records, where he recorded the soundtrack to Jonathan Livingston Seagull. In 1974, he released the album Serenade (songs: "Longfellow Serenade", "I've Been This Way Before"). In 1976, he released Beautiful Noise, produced by The Band's Robbie Robertson.
In 1977, he released an album I'm Glad Your Here With Me Tonight, which included the track "You Don't Bring Me Flowers". The song was covered by Barbra Streisand on her album Songbird, which led one disc jockey to combine the two in a virtual duet. The popularity of the virtual duet motivated Diamond and Streisand to record the real thing, which became a very large hit in 1978.
Diamond starred in The Jazz Singer in 1980, opposite Lucie Arnaz. Though the movie was not successful, the soundtrack was a hugely successful album, spawning the singles "America", "Love On The Rocks", and "Hello Again". This would be the apex of his recording career.