Veteran engagement in mental health treatment (MHT) remains low. Peer specialists (PS) are well positioned to implement interventions addressing barriers to MHT engagement, given their familiarity with the process. This study aimed to develop and assess the acceptability of a primary care-based, PS-delivered intervention to improve MHT initiation. Aim 1 utilized modified Delphi methods with a committee of 12 stakeholders (e.g., PS, psychologists, and veteran patients) who provided input on the proposed PS-delivered MHT engagement intervention. The proposed intervention components included questionnaires to identify barriers to engagement and targeted strategies for the barriers (e.g., motivational interviewing, cognitive restructuring). Aim 2 consisted of qualitative interviews with veterans entering MHT, focused on acceptability and feasibility, and gathered additional feedback for the intervention drafted in Aim 1. PS in primary care also reviewed the intervention and provided feedback. Results from Aim 1 demonstrated the acceptability of PS utilizing questionnaires in their work with Veterans, emphasized the importance of rapport building, and provided consensus on the identification of tailored treatment strategies. Veterans entering MHT (n = 9) reported that they were excited about the option of PS being involved in treatment engagement. PS (n = 18) also reported the overall acceptability of the intervention and provided feedback impacting the implementation of the intervention. Incorporating primary care PS into MHT engagement is acceptable. This study serves as the first step in developing a PS-delivered intervention to improve engagement in veteran MHT with input from a diverse group of stakeholders. Implications and future directions will be explored. (PsycInfo Database Record (c) 2024 APA, all rights reserved).