The 71-year-old, who starred in A Man For All Seasons and We'll Meet Again, begins filming with the Birmingham-based serial this week as the show celebrates its 10th anniversary on air.
York takes on the role of Alzheimer's sufferer Lorna Robson, an elderly friend and neighbour of Julia Parsons (Diane Keen).
Julia becomes embroiled in Lorna's story when she makes a shock discovery at the bottom of her garden.
The episode, titled 'Gibberish', is due to be screened on Monday, July 12 on BBC One.
This week, Doctors celebrates its anniversary with a five-part series of behind-the-scenes shows, Decade of Doctors. Fronted by series regular Keen, the episodes transmit all this week at 2.15pm, straight after the latest instalment of the medial drama.
Yesterday, DS revealed that former Doctor Who actress Annette Badland recently filmed another guest spot.
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