This study examined various functions of social support (i.e., tangible, esteem, belonging, and appraisal) were examined as protective factors for suicidal ideation in a sample of 273 active duty Air Force Security Forces personnel. Generalized linear regression analyses were conducted to determine if various social support functions were differentially associated with the presence and severity of suicidal ideation, both as main effects and as moderators of emotional distress. None of the four social support functions differentiated suicidal from nonsuicidal Airmen, but esteem support (i.e., feeling respected, encouraged, and valued by others) was associated with significantly less severe suicidal ideation (B = −.074, SE = .025, p = .003). A significant interaction of tangible support (i.e., access to material resources) with emotional distress indicated that emotional distress was associated with more severe suicidal ideation only among Airmen reporting low levels of tangible support (B = .006, SE = .003, p = .018). When considered concurrently, both tangible and self-esteem functions of social support are differentially associated with decreased suicidal ideation among Airmen, but belonging (i.e., having someone to do things with) and appraisal (i.e., having someone to talk to about problems) functions were not. Findings suggest that different aspects of social support affect suicidal ideation in different ways.