A silver sword worth £5,000 was stolen from Preston Grasshoppers Rugby Club.
The 3ft sword was stolen sometime between 3.30am and 3.35am on March 13.
In another incident on March 16 thieves stolen two mobile phones from the changing area of the club.
Police believe the incidents could be linked to a series of burglaries across the county including burglaries at Fylde Rugby Club and Blackpool Rugby Club.
Det Insp Warren Atkinson said: “While we aren’t sure that these burglaries have been committed by the same person or group of people they do show some similarities and we would warn other sports clubs to be mindful of who they trust valuables to and also to check on their security, such as checking that they have working CCTV, or consider installing some if they don’t already have it.”