Wellesley Island is traversed by Interstate Highway 81 to the Port of Entry located on the northeastern part of the island, adjacent to the Thousand Islands International Bridge, connecting the United States and Canada. Routes 100 and 191 also are on the island.

• American Narrows -- the branch of the St. Lawrence River passing to the south of Wellesley Island.
• Barnett Marsh -- A swamp in the south part of the island.
• Crow Island -- an small island off the north shore.
• Densmore Bay -- A bay on the south shore of the southeast peninsula.
• Eel Bay -- A large bay between Wellesley Island and Grindstone Island.
• Grenell Isle -- A smaller island southwest of Wellesley Island.
• Lake of the Isles -- A body of water connected to the St. Lawrence River, lying between the northeast and southeast peninsulas.
• Manhattan Group -- A cluster of small islands northeast of Wellesley Island.
• Murray Island -- A smaller island southwest of Wellesley Island.
• South Bay -- A bay on the southeast part of the island.

Communities on the Island

• Collins Landing
• Grandview
• Moore Landing
• Fineview
• Saint Lawrence Park
• Thousand Islands
• Westminster Park

Parks on the island