Gilbert is best remembered for the lyrics to the Oscar-winning song "Zip-a-Dee-Doo-Dah" from the film Song of the South, which he wrote with Allie Wrubel in 1947. He also wrote American English lyrics for the songs in The Three Caballeros featuring Donald Duck. To lovers of Brazil's Bossa Nova era, Gilbert is known as an opportunist who garnered English rights to some of the genre's most iconic songs. He also wrote the Andy Williams' 1965 hit, "...and Roses and Roses", and "Lost in Your Love" with Sidney Miller, to music by Bert Jay.
He married actress Janis Paige in 1962. They had a daughter, actress and singer Joanne Gilbert.