The actor, who played the fifth Doctor between 1981 and 1984, will play Mr Percival, the ringmaster of a circus which brings a large crowd to Poplar.
Davison's other notable credits include playing Tristan Farnon in the original TV adaptation of All Creatures Great and Small and roles in At Home with the Braithwaites, The Last Detective and Law & Order: UK.
Filming on the Call the Midwife Christmas special began in August, with a detailed COVID-19 protocol policy being implemented to ensure the safety of cast and crew.
The 90-minute episode is set at Christmas 1965 and will see plenty of drama, with Sister Monica Joan rushed to hospital and Trixie becoming incensed after receiving a subscription to a Marriage Bureau as a Christmas gift.
The arrival of the Circus in Poplar is also set to play a major part in the special, with the event providing an exciting adventure for Nurse Crane.
On returning to filming last month, series creator Heidi Thomas said, "Everyone is overjoyed to be whisking the dust sheets off Nonnatus House and getting back to filming after lockdown.
"It is a particular thrill to be able to deliver the Christmas Special on time, just as we promised at the start of the pandemic.
"We are very much a family at Call The Midwife, and like families everywhere, we have missed each other.
"We will now be putting more love and energy into our work than ever and can't wait to share series 10 with our fantastic, loyal audience."
Earlier in the year Thomas had told Christmas special was an “absolute priority” and that the team was “determined” to deliver it, despite the coronavirus pandemic.that the
Davison joins a busy cast for the special, which also includes Jenny Agutter (Sister Julienne), Linda Bassett (Nurse Crane), Judy Parfitt (Sister Monica Joan), Fenella Woolgar (Sister Hilda), Ella Bruccoleri (Sister Frances), Helen George (Trixie), Laura Main (Shelagh Turner), Leonie Elliott (Lucille), Stephen McGann (Dr Turner), Cliff Parisi (Fred), Annabelle Apsion (Violet), Georgie Glen (Miss Higgins), Max Macmillan (Timothy), Daniel Laurie (Reggie) and Zephryn Taitte (Cyril).