Dion was pursuing a singing career in his early teens, and made his first TV appearance on a show called Teen Club in 1951. He later recorded "The Chosen Few" with a group called The Timberlanes. In 1957, DiMucci rounded up the best singers he could find and began rehearsing on the subways heading into Manhattan. They called themselves Dion and the Belmonts, after Belmont Street in the Bronx. The group included tenor Fred Milano, tenor Angelo D'Aleo and bass singer Carlo Mastrangelo. By 1958, the group had its first hit with the doo-wop sounding "I Wonder Why" (#22) followed by "No One Knows" (#19). The next year, the quartet reached #40 with "Don't Pity Me" before their break-through hit, "A Teenager in Love" (#5). In 1960, the hit parade continued with "Where Or When" (#3), "When You Wish Upon A Star" (#30) and "In The Still Of The Night" (#38).

Dion went solo in 1960 (the Belmonts did some more recordings on their own), moving from doo-wop to more R&B/pop-oriented tunes with great success. He handled himself with a suave, cocky ease on a long string of hits like "Lonely Teenager" (#12), "Runaround Sue" (#1), "The Wanderer"(#2), "Lovers Who Wander" (#3), "Little Diane" (#8), "Love Came To Me" (#10), "Ruby Baby" (#2), "Donna the Prima Donna" (#6) and "Drip Drop" (#6). These tunes cast him as either the jilted, misunderstood youngster or the macho lover, capable of handling anything that came his way.

By the mid-'60s, his heroin habit (which he'd developed as a teenager) was getting the best of him, and he did little recording and performing for about five years. When he did make it into the studio, he was moving in some surprisingly bluesy directions, which met with little success.

In 1968 he kicked heroin and re-emerged as a gentle folk-rocker, and scored a #4 hit single, "Abraham, Martin and John." The song was sort of an anthem for the times, asking why some of America's greatest leaders were killed in their prime. Dion would focus upon mature, contemporary material on his late '60s and early '70s albums, but a follow up hit never appeared. Although his material received positive critical feedback, he managed only moderate sales.

The folk phase didn't last long; in 1972 he reunited with the Belmonts, and in the mid-'70s cut a disappointing record with Phil Spector as producer. The kinds of music that Dion knew best, doo-wop and folk, were no longer in fashion and he quickly faded from view.

He's been recording and performing fairly often over the last two decades (sometimes singing Christian music) to indifferent commercial results. But his critical reputation has risen steadily since the early '60s, with many noted contemporary musicians showering him with praise and citing his influence.

Today, DiMucci continues to perform on the oldies circuit from time to time.