Abstract The US is poised for growth and investment in our mental health crisis system, with a national phone/text line launching, accompanied by new funding for crisis services. More than 600 Crisis Stabilization Centers (CSCs) across the US provide suicidal clients with a more comfortable and less costly alternative to Emergency Department (ED) care. In light of rising demand, there is an urgent need for feasible, effective, interpersonal, recovery-oriented interventions. This study adapts and tests a novel intervention for delivery prior to and after discharge from CSCs. THRIVE uses the Interpersonal Theory of Suicide as a framework to bolster social connectedness and counter perceived burdensomeness. Preliminary data shows promising results. However, CSC workflows and culture require context-specific adaptation. This study leverages the Model for Adaptation Design and Impact to adapt THRIVE for CSCs, test feasibility, acceptability, and appropriateness, and conduct a pilot RCT in two CSCs. The CSC-adapted intervention addresses interpersonal drivers of suicide risk and bolsters safety, recovery, and community linkage through: (a) a `belonging and giving' group during CSC stay, (b) recovery coaching calls for 4 weeks post-discharge, and (c) an optional phone app that provides reinforcement and resources for connection. The pilot will compare THRIVE + Discharge/Safety Planning (D/SP) to D/SP alone, examining the degree to which THRIVE engages the targeted mechanisms of change at one- and three-months post-discharge. Aim 1. Adapt THRIVE and complete CSC-specific manual using MADI. Aim 2. Test feasibility, acceptability, appropriateness of THRIVE for CSCs. CSC Guests (n = 20). 75% of guests will participate in a THRIVE group and at least one follow-up session within one month of discharge. Ratings of acceptability and satisfaction will be ≧ 75%. CSC Staff (n = 4). Fidelity ratings of audio recordings of group and coaching calls with be at least ≧ 75% for all staff who deliver THRIVE. CSC Administrators will rate acceptability and appropriateness of THRIVE for CSCs as ≧ 75%. Aim 3. Conduct a randomized pilot effectiveness trial (n = 162) to assess the effect of THRIVE on treatment initiation and on key interpersonal drivers of suicide – belongingness and burdensomeness. We hypothesize that CSC guests who receive THRIVE + D/SP vs. D/SP alone will have: H1: Higher rates of treatment initiation at 1 month and 3 months from CSC discharge. H2. Increased belongingness and decreased burdensomeness at 1 and 3 months after discharge. We will explore the effect of the intervention on treatment engagement, acute care psychiatric readmissions, and suicidal ideation and suicidal behavior over 3-month follow-up. At the end of the study, THRIVE for CSCs will be ready to test in an effectiveness trial for preventing suicidal behavior.