Attitudes towards sex and gender, including sexism, may be shaped by the Darwinian forces of intra-sexual competition and inter-sexual conflict. Contest behaviour is an expression of intra-sexual competition for resources, status and, ultimately, access to potential mates. The dynamics within a contest can also be changed depending on social factors. For example, men display increased aggressive behaviours when competing against other men, particularly when an audience is present. However, the presence of females as competitors and its impact on behaviours has not been fully explored. We used combat video games as a competition medium and a series of standardised psychometric tests to measure subject’s level of sexism and dominant behaviours. We employed a 2x2 factorial design; (male/female competitor) x (win/lose) and looked at the effects of contest outcome on explicit sexist and dominance attitudes and implicit attitudes towards traditional gender roles. We interpret the findings in the context of evolved competitive behaviours among males and sexual conflict theory concerning mating and the attainment of status.