Matt Smith portrays the titular Time Lord.
Coleman, 25, has had roles in the British soap "Emmerdale," the movie "Captain America" and the upcoming miniseries "Titanic."
"Doctor Who" executive producer Stephen Moffat said the actress will join the cast after current companions Amy and Rory, played by Karen Gillan and Arthur Darvill, leave the show later this year, EW.com reported.
"It's not often the Doctor meets someone who can talk even faster than he does, but it's about to happen," Moffat said in a statement. "Jenna is going to lead him on his merriest dance yet. And that's all you're getting for now. Who she's playing, how the Doctor meets her, and even where he finds her, are all part of one of the biggest mysteries the Time Lord ever encounters. Even by the Doctor's standards, this isn't your usual boy-meets-girl."