The 80-year-old, best known for playing Nora Batty in the sitcom, died last week after a short illness.
Reverend Alison Cox told mourners at St Mark's Church in Dukinfield that Staff was a good woman, saying: "She was cheerful, generous and supportive. I can't imagine life without her."
Also speaking at the service was friend and former Coronation Street actor Roy Barraclough, who said: "The general public had a huge affection for Kathy."
Co-star Peter Sallis last week claimed that the actress will be "terribly missed".