Previous research highlighting the role sexual selection may play in the evolution of human cooperation has yet to distinguish what qualities such behaviours actually signal. The aim here was to examine whether female preferences for male cooperative behaviours are because they signal genetic or indirect phenotypic quality. This was possible by taking into account female participants' stage of menstrual cycle, as much research has shown that females at the most fertile stage show greater preferences specifically for signals of genetic quality than any other stage, particularly for short-term relationships. Therefore, different examples of cooperation (personality, costly signals, heroism) and the mate preferences for altruistic traits self-report scale were used across a series of four experiments to examine females' attitudes towards cooperation in potential mates for different relationship lengths at different stages of the menstrual cycle. The results here consistently show that female fertility had no effect on perceptions of cooperative behaviour, and that such traits were considered more important for long-term relationships. Therefore, this provides strong evidence that cooperative behaviour is important in mate choice as predominantly a signal of phenotypic rather than genetic quality.