As NWA champion, Severn debuted in the World Wrestling Federation in 1998 during a story line where the NWA invaded the WWF. Severn also wrestled on NWA territories at the same time during his tenure with the WWF. Severn was first seen attacking The Headbangers when they were feuding with Bob Holly and Bart Gunn, who were a part of the NWA invasion. In his debut match, he defeated Flash Funk in quick fashion. He was briefly managed by Jim Cornette who commentated during his matches and helped "get him over". During his entrance, he and Jim carried his titles consisting of UFC/MMA championship belts and the NWA world's heavyweight title. Cornette stated that "He has so many titles he keeps some at home because he can't take them in the airport", which is why Dan brought his most prestigious championships. His character was portrayed as a heel (villain). Like Flash Funk, he defeated multiple opponents afterwards, the likes of Savio Vega and Mosh, in quick fashion and by showing some of his Mixed Martial style and ability. This led to a winning streak. The NWA invasion was brief and saw the debut of The New Midnight Express and a repackaged Jeff Jarrett. Barry Windham was also a member. Severn would tag team with these members from the stable. Severn would then leave the stable soon after to continue further singles competition on his own.