A beloved Catholic priest is recovering in hospital after a man pulled out a knife and stabbed the 48-year-old in front of shocked worshippers in Melbourne's northern suburbs.

Reverend Tomy Mathew was about to begin the 11am Italian mass at St Matthew's Catholic Church on Sunday when the man approached with what was believed to be a kitchen knife.

"You can imagine our shock," said one long-time volunteer at the parish, located on William Street in Fawkner.

"But the ambulance was here quickly and he just walked out to get into the ambulance."