Research analyzing social dynamics has shown that systems can be structured by individuals of different age, size, sex and reproductive state within a population. Extensive research on male–male interactions in crayfish has illustrated the mechanisms that underlie the agonism and social relationships that develop between conspecifics. Despite the wealth of knowledge on male–male interactions, there is a lack of knowledge on the role that reproductive state plays in modulating aggression between the sexes in crayfish. The purpose of this study was to investigate aggression between crayfish of different sexes and reproductive forms. Form I and II male crayfish were paired against glair and non-glair female crayfish in agonistic bouts. Fight outcomes, intensities and mating events were calculated from the paired interactions. Form I male crayfish won significantly more bouts with females than form II males. In addition, reproductive females won more bouts than non-reproductive males. Thus, reproductive state of the individual has a significant influence over the outcome and level of aggression within agonistic encounters. This finding may indicate that the individuals are approaching interactions with motivational states (reproductive needs versus resource acquisition).