Background: Marriage has been identified as a protective factor in relation to suicide among older adults. The current study aimed to investigate whether sense of belonging mediated the marital status-suicidal ideation relationship, and whether gender moderated the mediation model. It was hypothesized that the relationship between being widowed and lower levels of sense of belonging, and between lower levels of belonging and higher levels of suicidal ideation, would be stronger for older men than older women. Methods: A community sample of Australian men (n = 286) and women (n = 383) aged from 65 to 98 years completed the psychological subscale of the Sense of Belonging Instrument and the suicide subscale of the General Health Questionnaire. Results: The results supported the moderated mediation model, with gender influencing the marital status-sense of belonging relation. For men, widowhood was associated with lower levels of belongingness, whereas for women, marital status was unrelated to sense of belonging. Conclusions: It would appear crucial to develop and implement interventions which assist older men to find new ways to feel important and valued after the death of their spouse.