One in four veteran primary care patients suffers from a mental health condition; however, most do not receive any treatment for these problems. Mobile health (mHealth) can overcome barriers to care access, but poor patient engagement limits the effectiveness and implementation of these tools. Peers may facilitate patient engagement with mHealth. We designed a protocol for peers to support implementation of mobile mental health tools in primary care and tested the feasibility, acceptability, and clinical utility of this approach. Thirty-nine patients across two Veterans Affairs sites who screened positive for depression during a primary care visit and were not currently in mental health treatment were enrolled. Participants were scheduled for four phone sessions with a peer over 8 weeks and introduced to five mobile apps for a range of transdiagnostic mental health issues (stress, low mood, sleep problems, anger, and trauma). Pre/post phone interviews using quantitative and qualitative approaches assessed participants' self-reported app use, satisfaction with the intervention, symptom change (stress, anxiety, depression, insomnia), and progress with personal health goals. On average, patients reported using 3.04 apps (SD = 1.46). Per the Client Satisfaction Questionnaire, global satisfaction with the intervention was high (M = 25.71 out of 32, SD = 3.95). Pre to post participants reported significant improvements in their level of stress, based on a quantitative measure (p = .008), and 87% reported progress on at least one personal health goal. Findings support the feasibility, acceptability, and clinical utility of peer-supported mobile mental health for veterans in primary care. A randomized controlled trial of an adaptive version of this intervention is recommended. (PsycInfo Database Record (c) 2023 APA, all rights reserved).