This study aimed to investigate the effect of brief reminder-focused positive psychiatry and suicide prevention (RFPP-S) on suicidal ideation, posttraumatic stress disorder (PTSD) symptoms, and clinical outcomes among youths with PTSD treated in psychiatric emergency rooms.Methods: This study included youths with PTSD and suicidality who received either RFPP-S (N550) or treatment as usual (N5150). The Columbia Suicide Severity Rating Scale (C-SSRS), Clinician-Administered PTSD Scale for children and adolescents, University of California, Los Angeles Trauma Reminder Inventory, Patient Health Questionnaire-9, Positive Emotion, Engagement, Relationships, Meaning, and Accomplishment Scale, and positive psychiatry test batteries were administered at baseline, on day 2, and 1 week and 1 month after discharge.Results: On day 2, the RFPP-S group showed a greater reduction in PTSD symptoms (55%) and reactivity to trauma and loss reminders (80%) compared with the control group (10% for both) (p50.001). A significantly greater reduction in C-SSRS score for RFPP-S (80%), compared with treatment as usual (15%), was noted (p50.001), and RFPP-S showed more rapid stabilization (mean6SD52.060.5 days) and enhanced postdischarge follow-up (100%) compared with treatment as usual (5.062.0 days and 50%, respectively) (p,0.05). RFPP-S, but not treatment as usual, was associated with significant increases in well-being, flexible thinking, and coping skills (p,0.05). Hospital readmission due to suicidality 1 month after discharge was 0% for the RFPP-S group and 20% for the control group.Conclusions: RFPP-S was associated with reduced PTSD symptoms, enhanced coping skills while experiencing trauma reminders, adoption of safety skills, rapid stabilization of acute crises of PTSD with suicidality, adherence to post-emergency room visits and treatment, and favorable clinical outcomes.