Using resemblance cues, people can identify highly related kin and treat them preferentially over less related or unrelated individuals, all else being equal. However, differences in degrees of resemblance can occur even within particular kin categories, such as siblings. We hypothesized that the level of perceived resemblance between siblings will predict sibling investment. Eighty Israeli students who had at least 2 full siblings filled out questionnaires regarding the younger sibling who was nearest to them in age. We found that sibling resemblance was positively associated with sibling investment, with emotional closeness serving as a mediator for the relationship between resemblance and investment. The results support the hypothesis that perceived resemblance to a younger sibling predicts investment in that sibling.