BackgroundCriminal legal system-involved individuals with serious mental illness (SMI) experience more challenges accessing mental health and other community services than those without a history of criminal legal system involvement. A formative qualitative study was conducted to explore feasibility and acceptability and inform the adaptation of a mental health peer navigation intervention for individuals with SMI reentering the community after jail incarceration.MethodsIn-depth qualitative interviews and focus-group discussions were conducted with mental health peer navigators (i.e., certified mental health peer support specialists, peer recovery coaches) and individuals with lived experience of SMI and criminal legal system involvement (N = 20 total). Data were analyzed using applied thematic analysis.ResultsFour major themes emerged: (1) Feasibility and acceptability of peer-provided services: all participants reported that peer navigation services would be feasible and acceptable for individuals with SMI reentering the community after jail incarceration; (2) roles of peer navigators in addressing barriers to care: peers can address barriers to care experienced during community reentry and contribute towards service linkage/engagement; (3) shared identity and combating stigma: having a shared identity with peer navigators may minimize the impact of stigma and make it easier for clients with multiple marginalized identities to seek support; and (4) peer navigator skills and recommendations for the planned program: essential peer navigation skills include authenticity, reliability, active listening, advocacy, trauma-informed care, motivational interviewing, and empathy. Recommendations for the planned program include initiating services while clients are in custody, emphasizing the voluntary nature of peer support, knowing the limits of a peer navigation intervention, and offering support for peer navigators while on the job.ConclusionParticipants saw peer navigation services for individuals with SMI with criminal legal system involvement as potentially feasible and acceptable. Such programs may enhance their impact by offering supportive supervision, emphasizing the voluntary nature of the service, and acknowledging recovery as a self-directed endeavor.