On August 22, 1908, Gilcrease married Belle M. Harlow, a member of the Osage Nation. He fathered two sons with Belle: William Thomas Gilcrease, Jr., who was born on July 23, 1909 in Oklahoma and died on March 16, 1967 in Nacogdoches, Nacogdoches County, Texas, and Barton Eugene Gilcrease, who was born on April 12, 1911 in Tulsa, Oklahoma, and died on September 25, 1991 in San Antonio, Bexar County, Texas. The couple's marriage ended in divorce in 1924. On September 3, 1928, he married 19-year-old Norma Des Cygnet Smallwood, the former Miss Tulsa and Miss America 1926.