Developed by Bossa Studios, the Facebook video game adaptation of the BBC television series features real-time co-operative play, allowing players to explore quests with six other friends.
The role-playing social game involves players travelling across Camelot, fighting monsters and levelling up.
Bossa Studios' creator-in-chief Imre Jele had previously told Digital Spy that Merlin: The Game will also be accessible to those unfamiliar with the show.
"Not everyone knows the TV show," he said. "So we've designed it in a way that if you know the show, you're going to find a lot of little things that are relevant for the game."
Merlin: The Game can be accessed on the title's official website.
A Nintendo DS game based on Merlin will be available later this month.
Watch a trailer for Merlin: The Game below: