Background: Veteran suicide rates are 1.5 times higher than the general population rates and are especially high following discharge from an inpatient mental health unit when up to a third of patients do not receive timely outpatient follow-up care. Technology-based interventions are a scalable approach to provide additional support to patients during these high-risk transitions. The Virtual Hope Box (VHB), a mobile phone application (app) developed by the Department of Defense (DoD) and VA, allows patients to access reasons for living and coping tools regardless of their location. VHB was effective for improving coping self-efficacy in a small randomized controlled trial; however, no studies have been adequately powered to examine VHB’s effectiveness for suicide attempts. Additionally, knowledge and use of the app is low according to a preliminary study of mental health inpatients, calling for new strategies to facilitate greater use and impact of the VHB app. Significance: The suicide rate among Veterans rose 35.9% from 2001 to 2019, leading to VA to make suicide prevention a top clinical priority. We developed an intervention, which includes the VHB app and its enhanced facilitation (VHB-EF), with the aim of reducing Veteran suicide attempts. Developing and implementing effective strategies to reduce suicide attempts post-hospitalization is also a research priority within this RFA. Innovation/Impact: We developed VHB-EF to provide awareness, active engagement, and support of VHB with the aim of reducing suicide attempts post-hospitalization. This study will be the first to test the effectiveness of VHB-EF on suicide attempts and may improve safety after discharge. It will examine potential intervention mechanisms, according to self-efficacy theory and the theory of planned behavior, while also considering ultimate implementation and scalability of the VHB-EF through provider and Veteran feedback. Specific Aims: Aim 1: Determine the effectiveness of VHB-EF for reducing suicide attempts. Aim 2: Examine the intervention mechanisms by measuring the effects of VHB-EF on 1) reasons for living, and 2) self-efficacy to (a) cope and (b) refrain from suicide attempts. Exploratory Sub-aim 2: Examine whether higher reasons for living and self-efficacy partially mediate the effect of VHB-EF on suicide attempts over 6 months. Aim 3: Assess the determinants (barriers and facilitators) of VHB-EF adoption to inform future implementation and sustainability of VHB-EF across the VA. Methodology: A randomized effectiveness-implementation Hybrid Type I trial will be conducted at two VHA inpatient mental health units. We will randomize 928 Veterans hospitalized after a suicidal crisis to either VHB- EF or Enhanced Usual Care (EUC). The VHB-EF includes a single session on the unit that educates Veterans on app purpose for suicide prevention, loads the app on their personal phone, provides practice of each app component, and discusses strategies to enhance app usage a...