This study examines the effects of social capital as it affects men's mental health in the context of work–family balance. Multivariate analyses of data from National Family Research of Japan 2008 have revealed the following. First, the social capital that men receive from their spouses was found to have a direct effect on their distress. The effect of social capital from family other than a spouse does not have a direct effect on men's mental health. Second, only social capital from a spouse was observed to provide a buffering effect. This result implies that, in contemporary Japan, social capital derived from the spouse functions satisfactorily as a bulwark to mitigate the negative effects that the experience of role conflict between work and family has on men's mental health. Finally, the study examines the effect of social capital with reference to social support theory. Subsequent research might usefully focus on varieties of social capital other than those covered in the current study, which will leverage the unique potential of social capital by examining techniques and units of analysis.