Abstract Males of Sphenarium purpurascens (Charpentier) (Orthoptera: Pyrgomorphidae) can spend up to 18 d mounting a female and mating repeatedly during this period. However, both females and males are polygamous. In this study, we assessed the potential benefits of multiple matings for females, with the same male or with different males. Furthermore, we evaluated the capacity of the male to assess the risk of sperm competition. The fecundity of females mated repeatedly with a male was not affected by the number of matings, but it increased by having prolonged matings. Moreover, polyandry did not increase fecundity of females. Females mated with one male produced more eggs and heavier clutch than females mated with two males. We also found that the second male that mated a female spent more time mating and guarding her than the first male, suggesting that male investment may change according to the risk of sperm competition.