Abstract: Introduction: Active duty service members who are psychiatrically hospitalized for suicide are at the highest risk for suicide death following discharge. It is essential to test brief treatments that can be delivered during the short length of stay in inpatient psychiatry. Written Exposure Therapy, a brief treatment for posttraumatic stress disorder (PTSD), was augmented with Crisis Response Planning (WET + CRP) to address PTSD and suicidal ideation (SI). Methods: This randomized controlled trial evaluated the efficacy of the WET + CRP plus treatment as usual (n = 47; TAU) compared with TAU alone (n = 48) in reducing SI, PTSD symptoms, and rehospitalization among suicidal patients with at least moderate PTSD symptoms admitted to an inpatient psychiatric unit. PTSD symptoms and SI were assessed with clinician-administered interviews and self-report. Results: Participants were primarily male (61.1%) and active duty/reserve (93.7%). There were no significant group differences in clinician-assessed SI presence and PTSD symptom severity (the primary outcomes) or self-reported SI severity. WET + CRP demonstrated significant reductions in self-reported PTSD symptom severity compared with TAU; these reductions were the strongest during the month following discharge. Conclusions: Although the findings were not fully consistent with hypotheses, WET + CRP is feasible to deliver to suicidal, psychiatrically hospitalized service members and warrants additional study.