The frequency of eating with friends and/or family (i.e., eating together) has been reported to have a positive effect on mental health. More specifically, the reception of psychological support from others (e.g., my friend calms my feelings) and the provision of psychological support for others (e.g., I tell my friend that the situation also has positive aspects) during the shared meal times are proposed to mediate the relationships between eating together frequently and mental health. However, these possibilities are not yet confirmed. The present study examined whether reception of psychological support and/or provision of psychological support mediate the relationship between eating together frequently and mental health. In total, 135 Japanese undergraduate students were asked to complete a questionnaire regarding the frequency of eating together, reception of psychological support, and provision of psychological support. In addition, we measured stress responses and positive moods in daily lives as indices of mental health. The path analysis showed that eating together frequently had a positive effect on the provision of psychological support and daily positive mood, but not for stress responses. In addition, the provision of psychological support mediated the relationship between the frequency of eating together and daily positive mood. However, the reception of psychological support did not mediate the relationship between frequency of eating together and mental health. Based on these results, it can be considered that eating together with friends and family frequently promotes the provision of psychological support for others during meal, which improves mental health in turn.