Many postpartum women experience sexual dysfunction, characterised by reduced sexual motivation and libido, and pain during intercourse. Menstruation is also suppressed in breastfeeding women (lactational amenorrhoea). Lactational amenorrhoea has been discussed in an evolutionary context due to its positive impacts on birth spacing. In contrast, postpartum sexual dysfunction has not been viewed through an evolutionary lens. Might postpartum sexual dysfunction also be under selection? We discuss possible evolutionary explanations for postpartum sexual dysfunction. In particular, we suggest that sexual conflict, a widespread phenomenon that occurs when the evolutionary interests of males and females diverge, may be a cause of disrupted postpartum sex. This sexual conflict-based explanation generates predictions relevant to the health and well-being of new mothers that warrant testing.