An evolutionary perspective yields fresh insights into the nature of human friendships and the emotions associated with these relationships. This approach sheds light on how specific types of friendship would have benefitted ancestral humans in the currency of natural selection—reproductive success—as well as in the currency of subjective well-being. This chapter outlines hypothesized ancestral functions of friendship, and discusses why immersion in friendships results in positive emotions such as happiness. We also review the empirical literature on different friendship types, drawing attention to the unique profiles of costs and benefits that characterize each type of friendship. In light of the various fitness-benefits and challenges that these relationships can pose, we propose evolutionarily inspired strategies for individuals to reap the benefits of friendships while simultaneously minimizing the costs they impose. In this way, we hope that an evolutionary approach not only augments our basic scientific understanding of these fundamental social relationships, but also contributes to the practical objective of enhancing friendships and maximizing their happiness yield.