Karen Gillan (Amy Pond) and Arthur Darvill (Rory Williams) will both exit the sci-fi drama midway through the new run.
"It's thrilling and exciting to be back and working with two of my closest friends," said Matt Smith, who returns for his third full series as The Doctor.
Gillan added: "It's just brilliant to be back on the TARDIS with Matt and Arthur for our craziest adventures yet."
It has also been announced that Sherlock star Rupert Graves and Harry Potter actor David Bradley will appear in the new episodes.
The pair join The Fast Show's Mark Williams, whose casting was reported on Tuesday.
Doctor Who will return to BBC One in the autumn.
> Doctor Who to film new series in Spain?
Watch Matt Smith discuss his future on Doctor Who below: