Military members and Veterans at-risk for suicide are often unlikely to seek behavioral health treatment. The primary aim of this study was to test the efficacy of brief CBT for Treatment Seeking (CBT-TS) to improve behavioral health treatment utilization among U.S. military service members and Veterans at-risk for suicide. A total of 841 participants who served in the U.S. military since 9/11 and who reported suicidality but were not in behavioral health treatment were recruited to participate in this trial. Participants were randomly assigned to either brief CBT-TS delivered by phone or an assessment-only control condition. Follow-up assessments were conducted at baseline and months 1, 3, 6, and 12 to track treatment utilization and symptoms. CBT-TS resulted in significantly greater behavioral health treatment initiation within 1 month compared to the control condition (B = .93, p < .001); and the higher treatment initiation persisted for 12 months post intervention. This study employed a low-cost, easily implementable one-session intervention administered by phone. The study provides evidence that CBT-TS is efficacious in promoting behavioral health treatment initiation in an adult population at risk for suicidal behavior and showed enduring benefits for 6-12 months. CBT-TS provides a unique strategy for treatment engagement for at-risk adults unlikely to seek treatment. Clinicaltrials.gov NCT05077514. © 2023. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.