The New York Post published photos Sunday of dressed-up guests arriving at the small ceremony at a chapel that the couple, who have been together since 2015, had built on their estate.
Stefani confirmed last month that her family had thrown her a bridal shower.
Shelton was previously married to country singer Miranda Lambert from 2011-15.
Stefani filed for divorce from musician Gavin Rossdale, her husband of 14 years, in 2015.
She and Rossdale are the parents of sons Kingston, 15, Zuma, 12, and Apollo, 7.