The man had left the medals on a work surface to clean before leaving his home in Wootton Park, Bristol, only to find on his return that they had vanished.
It is thought someone entered the house via a rear door on the afternoon of 22 June.
Avon and Somerset Police are appealing for help in tracing the items.
Among the collection of medals was a bronze 1939-45 star, a bronze France and Germany star and a police long service medal. The medals were were engraved with the victim's name, the regimental number 2666006 and 5th Battalion Coldstream Guards.
A silver and green French Legion d'Honneur medal  - the highest decoration bestowed by the French state - and a black wallet with gold lettering in the bottom right corner were also taken.
Anyone with information is urged to call 101 and quote reference number 5216151507.

Anthony and Yvonne Pardoe travelled round the world collecting the items which date from the 1900s to the 1950s.
Buyers from the US, Israel and Holland attended the auction at Bearnes, Hampton and Littlewood, Exeter.
It was thought to be "the fourth largest collection in the world" director Christopher Hampton said.
A US Navy Helium diving helmet took top price for a single item at £8,000, followed by an Italian helmet which took £7,200.
Auctioneer Brian Goodison-Blanks said: "When you start looking back and start thinking, 'well how did these guys actually go down with these diving helmets on', it looks incredible."
He said the colours and patterns of the helmets also sparked "that emotive Jules Verne feeling" in people and "just look wonderful".
A 91-year-old war veteran had his six medals stolen from his home while he went on a shopping trip.
[NEXT_CONCEPT]
A lifetime's collection of hundreds of diving helmets and equipment has fetched £476,000 at auction.