The assault was branded "callous and cowardly" by police who are appealing for witnesses to come forward.
The victim had just collected his winnings from a bookies last night and was walking through the car park of the Immaculate Conception Chapel in Glasgow's Maryhill Road.
A man grabbed him, dragged him to the ground, punched him on the body and stole his wallet. The suspect then walked from the scene along Maryhill Road at about 6.20pm.
Detective Constable Alex Cameron said: "This was an extremely callous and cowardly attack on a vulnerable man who had no chance against the suspect.
"The victim is an ex-soldier who has fought for his country, and to be dragged to the ground and robbed – on his way to mass is deplorable.
"He is also hard of hearing and would have been caught completely unaware. Thankfully he hasn't been injured, however he is naturally suffering from shock."
Detectives have been speaking with parishioners who were also attending the mass, checking with local shop-keepers and also reviewing CCTV from in and around the area.
Dc Cameron added: "The victim had been in nearby William Hill bookmakers prior to the attack to collect a small winning. Therefore the suspect may have witnessed this and followed him to the chapel.
"We will be looking at available CCTV from the bookmakers, but would ask anyone who was in William Hills in 1957 Maryhill Road and who perhaps saw the suspect there to contact us.
"I would also appeal to anyone who was in the area of the Immaculate Conception Chapel and who saw anything at all to come forward. It is imperative we trace this man."
The suspect is described as a white male, 35-40 years, 5ft 4ins tall, slim build, gaunt appearance and was wearing black trousers and a black, possibly shiny, hoodie.