Introduction: Service users’ involvement as cofacilitators of mental health trainings is a nascent endeavor in low- and middle-income countries, and the role of families on service user participation in trainings has received limited attention. This study examined how caregivers perceive and facilitate service user’s involvement in an antistigma program that was added to mental health Gap Action Program (mhGAP) trainings for primary care workers in Nepal. Method: Service users were trained as cofacilitators for antistigma and mhGAP trainings delivered to primary care workers through the REducing Stigma among HealthcAre ProvidErs (RESHAPE) program. Key informant interviews (n = 17) were conducted with caregivers and service users in RESHAPE. Results: Five themes emerged: (a) Caregivers’ perceived benefits of service user involvement included reduced caregiver burden, learning new skills, and opportunities to develop support groups. (b) Caregivers’ fear of worsening stigma impeded RESHAPE participation. (c) Lack of trust between caregivers and service users jeopardized participation, but it could be mitigated through family engagement with health workers. (d) Orientation provided to caregivers regarding RESHAPE needed greater attention, and when information was provided, it contributed to stigma reduction in families. (e) Time management impacted caregivers’ ability to facilitate service user participation. Discussion: Engagement with families allows for greater identification of motivational factors and barriers impacting optimal program performance. Caregiver involvement in all program elements should be considered best practice for service user-facilitated antistigma initiatives, and service users reluctant to include caregivers should be provided with health staff support to address barriers to including family.