The standalone multiplayer mode will be available to download from the PlayStation Store from February 28.
The free-to-play experience features all of the game's maps, but adds a level cap and limits the number of skills and weapons available to each user.
To enjoy the full multiplayer mode, North American users will have to pay $14.99. European prices and launch dates are yet to be confirmed.
Killzone 3 was released as a PS3-exclusive last February. It went on to become the 14th fastest-selling Sony title in first-week UK sales.
A port of the 2004 PlayStation 2 original was due to be released on the PlayStation Store in January. The game has since been delayed indefinitely.
> Read our review of Killzone 3
Watch a trailer for Killzone 3 below: