Introduction: Engagement in Veteran’s healthcare administration (VHA) mental health treatment (MHT) remains low. There is no consensus on a universal predictor of engagement—thus a personalized intervention approach may be appropriate. Given their familiarity with the engagement process, Peer Support Specialists (PSS) are well-positioned to implement interventions addressing barriers to MHT engagement. This study aimed to develop, and assess the acceptability of, a PC-based, PSS-delivered intervention to improve MHT initiation. Methods: Intervention development involved two stages. The first stage used modified Delphi methods with a committee of 12 stakeholders (including PSS, psychologists, Veteran patients, and others) who provided input on the intervention. The second stage consisted of qualitative interviews with Veterans entering MHT (n=30) and focused on acceptability of the intervention drafted in stage one. Additionally, VHA PSS (n=30) in PC reviewed the intervention and provided feedback. Results: Results from the first stage demonstrated the acceptability of PSS utilizing assessments in their work with Veterans, and emphasized the importance of rapport building and of differentiating the skill of PSS from those of clinicians. The first stage concluded with the committee reaching a consensus on four assessments to identify barriers to engagement with MHT which will be utilized in the intervention. Results from the second stage, which is still in progress at time of abstract submission, will also be presented. Discussion: Incorporating PC PSS into MHT engagement has shown to be acceptable. This study serves as the first step in developing a PSS-delivered intervention to improve engagement in VHA MHT with input from a diverse group of stakeholders. Implications and future directions will be explored.