Subscriptions for the Star Wars-themed MMO total 1.3 million, down from 1.7 million in February, reports CVG.
Electronic Arts has cited lower numbers of trial players as the reason for the decline, suggesting that the game is on par with the likes of Madden and The Sims in terms of performance.
"The substantial portion of the decrease was due to lower numbers of trial players, upping the percentage of paying subscribers," explained EA's Ken Barker.
"Some of those casual customers have gone through a billing cycle and have decided not to subscribe to the game," added EA's Frank Gibeau.
The figures were revealed during an EA financial call, in which the company confirmed new Dead Space and Need For Speed titles, and promised to invest $80 million (£49m) in next-generation software.
Star Wars: The Old Republic has been recognised by disability charity AbleGamers Foundation , and has been inducted into the Guinness Book of World Records as the 'Largest Entertainment Voice Over Project' of all time since its December 2011 debut.
The game is available now exclusively for PC.
> Read Digital Spy's review of 'Star Wars: The Old Republic'
Watch a trailer for Star Wars: The Old Republic below: