Lifetime history of suicide attempts is associated with inflammatory mechanisms, severity of depressive symptoms, and childhood trauma. This cross-sectional study enrolled 54 suicide attempters and 154 nonsuicide attempters. All individuals were assessed through a questionnaire, a structured clinical interview, scales, anthropometric measures, and laboratory biomarkers. Individuals with a history of lifetime suicide attempts showed significant positive correlations regarding soluble tumor necrosis factor receptor 1 and severity of depressive symptoms (p = 0.013), interleukin-1 receptor antagonist and severity of depressive symptoms (p = 0.04), and absenteeism from work and childhood physical abuse (p = 0.012). Suicide attempters also experienced more childhood trauma (sexual abuse, physical abuse, emotional abuse, emotional neglect, and physical neglect) compared with nonsuicide attempters. IL-4 levels were significantly lower in individuals who attempted suicide than in nonsuicidal individuals. Lifetime suicide attempts in major affective disorders were associated with childhood trauma and proinflammatory and anti-inflammatory cytokines.