Born in Hope Valley, Rhode Island, he lives with his parents Bill and Fran Gilman and his younger brother Colin.

At a young age he attracted the attention of a local vocal coach, Angela Bacari, who later became his manager. He met and worked with Ray Benson of (Asleep at the Wheel) who helped record demos, including "Roly Poly". He was then signed to Sony Music Nashville.

His 2000 debut album, One Voice, crossed over into the top 40 airplay. The album was certified gold after 4 weeks and later classified with double-platinum status and earned Gilman a Grammy nomination.

He was given entry into Guinness Book of World Records for the youngest singer to have a #1 country album, eclipsing the record set by 1960's star Brenda Lee. [citation needed]

Billy's first televised performance was of him singing "Roly Poly" with Asleep at the Wheel at the ACM awards.

Gilman has appeared on various talk shows, such as The Oprah Winfrey Show as well as performing at the opening ceremonies of the 2006 International Career Development Conference in Dallas, TX and the 2007 International Career Development Conference in Orlando, FL. Both conferences were held by the DECA high school marketing education club. He performed at a benefit for The Station nightclub fire.

He is the national youth chairman for the Muscular Dystrophy Association and is on the Muscular Dystrophy Association's Telethon every year as a co-host.