The island has an area of 150 square kilometres (58 sq mi).[5] It is separated from mainland North America on the south by the Shippagan Gut with the island forming Lameque Bay, Shippagan Harbour and Shippagan Bay west of this channel. The island is separated from Miscou Island on the north by the Miscou Channel, with both islands forming Miscou Harbour.
The Shippagan Gut is bridged between the town of Shippagan on the mainland to the local service district of Chiasson-Savoy on Lamèque Island by a 1,000-metre (3,300-foot) combination causeway-bridge with a lift bridge over a navigation channel for small craft.