After studying music in Montreal, Mills joined the Bells in the late '60s. Although the Bells did perform some of his songs, Mills left for a solo career in 1972. Released in the same year he left the group, "Love Me, Love Me Love" was his first solo record. The single was a hit in Canada and made some headway in the U.S., reaching number 46. Although he followed the single with several minor hits in Canada, his audience continued to shrink and he was left without a record contract by 1974.

Undaunted, Mills recorded and released Music Box Dancer with his own money in the mid-'70s. In 1979, an executive at Polydor Records heard the record and believed that the title track had hit potential, so he persuaded the company to release the song as a single. "Music Box Dancer" was a surprise hit, climbing to number three on the American charts. Following the success of the single, the album was also re-released. Like the single, the album was also a hit, reaching number 21.

Mills released another album, Prelude to Romance, in the U.S. in 1981 and it was a minor hit. Nevertheless, the album wasn't big enough of a hit from him to keep his U.S. record contract and after its release, he was only left with a Canadian contract. Mills continued to record into the '90s. In the course of his career, he has released over ten albums.