Which company developed Assassin's Creed II?

Ubisoft Montreal developed Assassin's Creed II.

The Canadian studio created the sequel after developing the original Assassin's Creed. Ubisoft Montreal expanded the series with Ezio Auditore's longer character arc, a broader Renaissance setting, improved social stealth, and additional systems such as property investment and equipment upgrades.

Ubisoft Montreal is one of the major studios within Ubisoft's international development network. Other Ubisoft teams later led different Assassin's Creed projects, including Ubisoft Quebec on Assassin's Creed Odyssey and Ubisoft Sofia on Assassin's Creed Liberation. Those associations can make studio answers easy to confuse.

Assassin's Creed II launched in 2009 for PlayStation 3 and Xbox 360, followed by Windows and other versions. It became one of the most commercially successful and critically praised entries in the franchise.