According to TVGuide.com, the actress will star as one of Dr. Derek "McDreamy" Shepherd's four sisters in two episodes that will air in December.
Embeth Davitz and Caterina Scorsone have already appeared as Shepherd's siblings in previous episodes.
Campbell and Dempsey have worked together in the past. The pair co-starred in horror film "Scream 3." The actress is currently starring in the Encore mini-series "Titanic: Blood and Steel."