Releasing next spring for £11.99 ($19.99), 'Rise of the Hutt Cartel' will be available five days in advance for customers who pre-order before January 7.
Copyright: EAPre-order customers will also secure preferred status, while subscribers will receive a 50% discount.
The 'Rise of the Hutt Cartel' introduces a brand new story in which the Hutt challenge for control of the galaxy.
In addition to an increased level cap of 55, the expansion also introduces the alien planet of Makeb, which is described as a "vibrant alien landscape".
Star Wars: The Old Republic introduced a free-to-play option in November.
The free-to-play option launched alongside the Cartel Market and an in-game reward scheme for existing subscribers.
Free-to-play users have full access to the game's story content and all eight classes up to and including level 50. However, players only have access to three of the playable races during character customisation - humans, zabrak and cyborgs.
Players are also limited to three Flashpoints, Warzones and Space Missions each week.
The restrictions can be bypassed through in-game purchases using the new Cartel Coin currency. For Flashpoints, Warzones and Space Missions, players can purchase a weekly premium pass to gain temporary unlimited access.
> Read Digital Spy's review of Star Wars: The Old Republic
Watch a trailer for Star Wars: The Old Republic below: