Epibiotic interactions between macroalgae and crustaceans have rarely been described. We examined the interaction between the mole crab, Emerita analoga and the opportunistic algae Enteromopha spp. in a sandy beach of the central coast of Peru. Enteromorpha spp. was found fouling the carapace of the mole crab that provides the only stable substrate to spore settlement in the beach environment. Epibiosis prevalence was up to 2.1%, and affected mainly larger, ovigerous females. Prevalence presented a seasonal pattern, with peaks during summer. Mole crab body condition was higher when fouled, whereas fecundity was not affected. Fouled mole crabs burrowed at lower speed, which was reversible by the removal of epibiotic algae. The burrowing depth was not affected by epibiosis. Contrary to the expected, the effects of algal epibiosis on demographic and life history parameters of mole crabs, with the exception of body condition, were mainly neutral but important on behavioural traits.