Dempsey, who plays Dr. Derek Shepherd on the popular ABC drama, was sponsored by the Avon Foundation in this weekend's Daytona International Speedway race, the Jacksonville (Fla.) Times-Union reported Sunday.
The actor's dalliance in auto racing is in support of the foundation's ongoing fight against breast cancer, a disease his mother once had. He also has opened the Dempsey Center for Cancer Hope and Healing in Maine.
"This is such a separate thing from the show and everything else that I do," Dempsey said prior to the start of the endurance auto race Saturday. "This just says a lot, I think, about the racing community in general. You see a lot of cars out there working in different charities and giving back to the community."
Dempsey said his hectic TV and movie career gave him little time to hone his driving skills.
"I wish I had more time to try and train," he told the Times-Union. "You need to train mentally, physically. More seat time is needed, more testing."