City Island is a large island off the coast of Orchid Bay. City Island is heavily infected with Fusion Monsters. The ruins of Jump City can be found here, as well as the wrecked Titans Tower (and hence also the portal to the Watchtower). On the far side of the island there is a mountainous area, featuring such sections as Fearless Falls, Blazing Bridge, and Chilled Cliffs. There is a KND fortress there called Fort Forte: there is a KND S.C.A.M.P.E.R. in the fortress that will take players to City Station, Peach Creek Commons, Mount Blackhead, Forsaken Valley, Hunter's Nest, and Dark City (one-way), as well as Monkey Skyway Agents who will take them to the Wattzap Dock in City Peninsula.
During the Lunar New Year Event, Goat and Nelliel appear in City Island to give out the Lunar New Year Mission "Year of the Goat".
- City Island was added to the game only in June of 2012, at the same time as City Peninsula.
- The area becomes available only after the player has "beaten" Fuse once; it is later revealed that he was able to regenerate after his initial defeat.