She was born Patricia Rowlands in Palmers Green, London, she attended a succession of convent schools throughout her childhood. At one an elocution teacher spotted her potential and encouraged her to pursue a career in acting. She applied for the Guildhall School of Music and Drama, and won a scholarship aged fifteen.

Patsy began her career at the Saville Theatre in Sandy Wilson's play Valmouth and then spent several years working in London as a regular member of the Players' Theatre. Other West End theatre credits include Semi-Detached with Laurence Olivier and directed by Tony Richardson (with whom she was to work often), Shut Your Eyes and Think of England, with Donald Sinden, The Seagull directed by Lindsay Anderson and When We Are Married for Ronald Eyre. She made a name for herself as a character actress in a range of stage and screen roles throughout the 1950s and 1960s. Patsy appeared in a total of nine Carry On films, all directed by Gerald Thomas. Initially a supporting player, her Carry On roles increased in size as she took the place of departing regulars in the later films of the series in the early and mid 1970s. Around this time she also played a recurring role in the long running sitcom, Bless This House, in which she appeared alongside Carry On regular Sid James.

Rowlands has recently appeared in several revivals of major musicals such as Oliver! and My Fair Lady, and her recent television credits include The Cazalet Chronicles, The Canterbury Tales, The Cater Street Hangman, Get Well Soon, and Vanity Fair for the BBC.

She died of breast cancer in a Sussex hospice at the age of 71. She had one son.