Preliminary evidence suggests military sexual trauma (MST) may be associated with increased risk for suicidal behaviors among active duty military personnel and veterans. Among National Guard personnel, a high-risk subgroup, MST and suicide risk have not received much empirical attention. To examine the association of MST with suicide ideation and suicide attempts among National Guard personnel. N = 997 National Guard personnel from Idaho and Utah participated in an anonymous online survey. Weighted analyses were conducted to minimize sampling bias. 9% of participants had a history of MST (6% of men, 28% of women). Among participants reporting MST, 68% reported a service member perpetrator and 44% reported a civilian perpetrator (12% reported both). A history of MST was associated with significantly increased risk for lifetime suicide attempt. MST remained a significant predictor of lifetime suicide attempt even when restricting the sample to the subgroup with a history of suicidal thoughts (n = 257, 27% of full sample). When adjusting for premilitary sexual victimization, MST was no longer significantly associated with lifetime suicide attempts, but premilitary sexual victimization was. The rate of MST among National Guard personnel is comparable to rates among active duty military personnel, although the perpetrators of MST are less likely to be service members. MST is a risk factor for suicide attempts, but premilitary sexual victimization is a relatively stronger risk factor.