It is situated on the south shore of the Saint Lawrence River at the top of a steep cliff.

The Historic Sites and Monuments Board of Canada installed a plaque at the base of the lighthouse in 1977, with inscriptions in French and English, which reads (in English): Built in 1858, this lighthouse is one of a series of tall, tapering towers erected on the Gulf of St. Lawrence and on Lake Huron by the Department of Public Works.

A powerful light 136 feet above high water served as a major coastal aid for shipping headed in the estuary of the St. Lawrence from the Gulf.

Cap-des-Rosiers has a humid continental climate (Köppen Dfb).

The average annual rainfall is 1,195.1 mm (47.05 in) with October as the wettest month.