Cancer productus has carapace teeth that are somewhat broad and rounded with teeth between the eyes of nearly equal size and shape. The carapace of C. productus is widest at the posterior-most tooth, up to 200 mm wide. The chelipeds are large with black tips. This species lacks serrations or projections on the ventral side of the claws. Adults have a brick red coloration throughout. The coloration of juvenile C. productus is diverse, often white, sometimes with red spots, or zebra striped.
Cancer magister has serrations on the dorsal side of the chelipeds and lacks black tips. Cancer gracilis has a single projection on the dorsal side of the chelipeds and also lacks black tips, and the widest point of carapace is at the second posterior-most tooth. Cancer oregonensis has black tipped chelipeds, but has large tubercles on the dorsum. C. oregonensis is also much smaller, such that a C. productus of similar size would generally have the striking juvenile coloration.