The 46-year-old singer and 40-year-old country star have hired famed wedding planner Jerri Woolworth after months of marriage rumors, TMZ reported Friday.
Woolworth, who is based in New York, has planned events for the NFL, the NHL and the Country Music Awards. Her office told the website they had "no comment" when asked about the celebrity couple.
Stefani and Shelton confirmed their relationship in November after splitting from their respective spouses, Gavin Rossdale and Miranda Lambert, earlier in the year. Stefani confessed in the September issue of Cosmopolitan that she was initially reluctant to start dating again.
"We were both having trust issues, as you would if you were us," she recalled. "I was like, 'I have so many problems. How can I now be getting into another potentially huge problem? What am I doing?'"
"Nobody except for my parents, the people involved, and whoever they told [know what happened with Rossdale]," the singer said. "Nobody would believe it if I could really say what happened. I went through months and months of torture."
Stefani had said in June that she and Shelton are "absolutely not" engaged. Shelton gushed about Stefani on Thursday's episode of Late Night with Seth Meyers, admitting he "can't believe" he's dating the star.