Portunites stintoni was a small swimming crab and one of the more mobile crustaceans of the London Clay sea. Its body plan belongs to a group adapted for active movement, allowing it to search a wider area for food than many strictly bottom-walking crabs.

It was probably an opportunistic predator and scavenger feeding on small invertebrates and carrion. Even a relatively small swimming crab would also have been useful prey for fish, linking the invertebrate community to larger predators.