The actress, who played the Yorkshire soap's Sarah Sugden between 1994 and 2000, is filming her one-off appearance this week for an episode due to air in July.
Spiro is taking on the role of Gill Ferry, the daughter of an elderly Alzheimer's sufferer named Lorna Robson. Lorna is introduced to the serial as a neighbour of regular character Julia Parsons (Diane Keen).
As previously revealed, veteran actress Susannah York is also filming with Doctors this week in the role of Lorna.
The pair's episode, titled 'Gibberish', is due to be screened on Monday, July 12 on BBC One. It will see Julia becoming embroiled in the lives of Gill and Lorna after making a shock discovery.
Doctors is celebrating its tenth anniversary this week and has been marking the occasion with Decade of Doctors, a five-part series of behind-the-scenes shows.
Earlier this week, DS revealed that former Doctor Who and Cutting It star Annette Badland had filmed a guest spot for the programme.