Gibson, 26, and Shepherd, 29, of Benton, La., exchanged vows in California on Saturday, the report said.
Shepherd's albums include "Ledbetter Heights" and "Live On."
He proposed to Gibson on New Year's Eve 2004 in Rome, according to the newspaper.
Gibson, 50, and his wife, Robyn, have seven children. Hannah is their oldest child and only daughter.
The wedding came almost two months after Gibson, 50, star of the "Lethal Weapon" movies and director of "The Passion of the Christ," was arrested for drunken driving in Malibu, Calif., on July 28.
Gibson has publicly apologized for an anti-Semitic tirade he unleashed when he was arrested. He has called the remarks "despicable."
In August, Gibson pleaded no contest to a misdemeanor charge in a deal that called for alcohol rehabilitation, fines and probation.