While smiling enhances women's facial attractiveness, the findings are inconclusive for men. The present study investigated the effect of smiling on male facial attractiveness for short- and long-term prospective partners using East Asian and European samples. In Experiment 1 (N = 218), where female participants rated male facial attractiveness, the facilitative effect of smiling was present when judging long-term partners but absent for short- term partners. This pattern was observed for East Asians as well as for Europeans. Experiment 2 (N = 71) demonstrated that smiling male faces engendered an impression suitable for long-term partnership (e.g., high ratings of trustworthiness) while neutral faces produced an impression suitable for short- term partnership (e.g., high ratings of masculinity). We discuss these results in terms of opposing evolutionary strategies in mate choice: heritable benefit versus paternal investment.