Jenkins has been cast in her first acting role in what has been billed as a "fun-filled and heartfelt festive story".
She said: "I'm over the moon to be involved in the Doctor Who Christmas special. I can't quite believe it as it's a part of the family tradition at the Jenkins household.
"I heard the news that I got the role on my 30th birthday and it was the best birthday present ever."
The hour-long show will, as usual, feature Matt Smith as The Doctor, with assistant Amy (Karen Gillan) and new husband Rory Williams (Arthur Darvill). The pair were seen at their wedding at the end of the most recent series last month.
The programme's executive producer, Steven Moffat, said: "We're going for broke with this one. It's all your favourite Christmas movies at once, in an hour, with monsters. And the Doctor. And a honeymoon.
"I've honestly never been so excited about writing anything. I was laughing madly as I typed along to Christmas songs in April. My neighbours loved it so much they all moved away and set up a website demanding my execution. But I'm fairly sure they did it ironically."
Previous Christmas specials have included roles for stars such as Kylie Minogue.
Ben Stephenson, controller of BBC drama commissioning, said: "Matt Smith and Karen Gillan captivated audiences in their debut series and Doctor Who's clever twist on the much-loved A Christmas Carol will thrill BBC One viewers this year with special guest stars Sir Michael Gambon and singing sensation Katherine Jenkins joining Amy and the Doctor for an unforgettable present."