The study examined whether informal and formal social participations may mediate the association between widowhood and depressive symptoms, and whether gender may moderate the mediated associations. The data consisted of men and women 65+ who participated in the 3rd wave of the Koran Longitudinal Study of Aging (KLoSA ; N = 4,146). Findings suggest that first, widowed older adults experienced significantly higer levels of depressive symptoms compared to their married counterparts. At the same time, the widowed individuals also reported more frequent contacts with family, friends, and neighbors (informal social participation), which contributed to narrowing the depression gap between widowed and married. Second, gender moderated the mediated association such that the mediating effect of informal social participation was significant only for older widowed women. Further, no mediating effect was found of formal social participation (participation in social, leisure, religious groups) for widowed and married regardless of gender. Previous studies indicated that social participation may be an important mediating factor that attenuates the effect of widowhood on depressive symptoms. Building on existing research, the present study highlighted theoretical rationales for potential gender differences in the way social participation may mediate the widowhood-depression linkage and evaluated statistically whether gender may moderate the mediated association.