This study analyzed whether the trematode Prosorhynchoides sp., at metacercaria stage, affects the sustained swimming capacity of the intertidal juvenile sea chub Girella laevifrons. Fifteen non-parasitized and 15 experimentally infested fish were used in this study. Wild fish were infested under laboratory conditions by cercaria from an infected mussel Perumytilus purpuratus. The parasite mainly infested the tail muscles of the fish. The maximum time of sustained swimming of each fish was measured through a swimming camera. Parasitized fish showed less time of sustained swimming and traveled less distance estimated than non-parasitized fish. This result was independent of fish body size, condition factor and trematode abundance. Therefore, Prosorhynchoides sp. affects the swimming capacity of juvenile G. laevifrons that might influence the migration and distribution of the fish.