He will effectively replace Bradley Walsh in the long-running sci-fi series when it returns later in 2021. Filming began in November. It will be the programme's thirteenth series since its 2005 revival.
In a statement released as the programme's Christmas special aired, he said: "If I could tell my younger self that one day I would be asked to step on board the TARDIS, I would never have believed it. It's an absolute dream come true to be joining Doctor Who and I couldn't wish for better company than Jodie and Mandip."
BBC One tease: "As he becomes embroiled in the Doctor's adventures, Dan will quickly learn there's more to the Universe(s) than he could ever believe. Travelling through Space and Time alongside the Doctor and Yaz, he'll face evil alien races beyond his wildest nightmares."
Chris Chibnall, Showrunner, says: "It's time for the next chapter of Doctor Who, and it starts with a man called Dan. Oh, we've had to keep this one secret for a long, long time. Our conversations started with John even before the pandemic hit. The character of Dan was built for him, and it's a joy to have him aboard the TARDIS."
Matt Strevens, executive producer for BBC Studios, says: "It's been a total joy having John join the cast and we've been having a lot fun on set already. We can't wait for you to meet Dan when the show returns later this year."
Piers Wenger, Controller of BBC Drama, says: "We are beyond thrilled to have John Bishop joining Doctor Who. Alongside Jodie Whittaker and Mandip Gill, John is a wonderful addition to the show and we have no doubt that Series 13 is going to be another thrilling set of adventures for the Doctor."
Here is a preview clip featuring Bishop: