The crab can often be found under rocks in the intertidal zone during low tide. The carapace is more square than triangular in shape. The color of the carapace is mottled, and ranges from green to purple to orange-brown. The legs have a distinct banding pattern of alternating light and dark colors. The claws have a speckled pigmentation pattern.
Male crabs have a fleshy, bulb-like structure at the base of the moveable finger of the claws.
Juvenile crabs can be very small and difficult to identify. Hemigrapsus sanguineus will have ecological impacts in its new home. It eats different types of algae and animals. It may occupy habitats very similar to crabs that are native to the region. It may act as a food source for larger animals.