Chart-Track figures show that 1.8m games were sold in May, generating £45.5m in revenue.
The biggest-selling games were Rockstar's Max Payne 3 and Activision's Diablo 3, reports MCV.
Despite not shifting as many units as LA Noire and Red Dead Redemption, Max Payne 3 sales ensured Rockstar a third successive best seller for the month of May.
Diablo 3's success, meanwhile, guaranteed Activision was the number one ranked publisher by value.
Video game sales have been in decline this year, something that has baffled industry analysts.
Despite breaking first-week PC sales records, Diablo 3 was beaten to the top of the all-format chart by Max Payne 3.
> Read Digital Spy's Max Payne 3 review
> Read Digital Spy's Diablo 3 review
Watch a trailer for Diablo 3 below: