A specimen of a gladiator box crab, Acanthocarpus alexandri Stimpson, 1871, was captured off the northeast coast of Newfoundland during June 2009. This is the first report of the species in Canadian Atlantic waters, and represents a major northern expansion in the distributional range by approximately 800-900 kilometres. The known distribution of this western Atlantic species now extends from Newfoundland to Brazil, encompassing tropical, temperate, and sub-arctic marine ecosystems.