Guided by paternal investment theory (PIT), the current research examines the effects of fathers on daughters' expectations for men in adulthood, and the role of these expectations in mediating women's short-term (casual or uncommitted) sexual behavior. Using a genetically informed differential sibling-exposure design (N = 223 sister pairs from divorced/separated families), we found that developmental exposure to low-quality paternal behavior (but not paternal absence per se) predicted adult women's expectations for men as partners. For older sisters, who spent much of their childhoods living with their fathers, lower-quality paternal behavior predicted lower expectations for male investment in their relationships as adults. Moreover, lower expectations for men as partners predicted higher numbers of sexual partners (past and anticipated) among these women. By contrast, for younger sisters, who spent relatively little time coresiding with their fathers, no such effects of quality of paternal behavior were observed. The current work provides evidence that exposure to low-quality paternal behavior during development may help calibrate daughters' expectations for the behavior of male relationship partners, and these expectations may shape their sexual behavior in adulthood.