Collins played Samantha Briggs in the 1967 Doctor Who serial The Faceless Ones and was offered the chance to continue in the series as a new companion for the Doctor, but declined the invitation.
Other early TV credits include the UK's first medical soap Emergency Ward: 10 (1960), and the pilot episode and first series of The Liver Birds, both in 1969.
Collins first became well known for her role as the maid Sarah in the 1970s ITV drama series Upstairs, Downstairs, which was co-created by her co-star Jean Marsh. The character appeared regularly throughout the first two series, the second of which also starred her actor husband, John Alderton, with whom she later starred in a spin-off, Thomas & Sarah (1979), and the sitcom No, Honestly, as well as in a series of short story adaptations called Wodehouse Playhouse (1975-78). She also appeared alongside her husband John Alderton in the successful series co-narrated the animated British children's TV series Little Miss with him in 1983.
Pauline Collins returned to Doctor Who in 2006 becameing only the third actor to have been in both the original and new series of Doctor Who, appearing in the episode "Tooth and Claw" as Queen Victoria.