Young adults (age 18-35) living with psychosis (YA-P; schizophrenia spectrum disorders) have high rates of heavy cannabis use that are associated with long-term deleterious mental health and functional outcomes. Those early in the course of psychotic illness are especially vulnerable to the negative impact of cannabis on future recovery. There are no effective interventions that reduce cannabis in this group. Clinicians agree that heavy cannabis use is a significant problem for YA-P patients and report that effective, evidence-based interventions are sorely needed. Families have been identified as effective and influential treatment allies for YA-P, but often, cannabis is a highly contentious topic that can lead to interpersonal conflict. Such conflict increases risk for psychotic relapse and is associated with non-change of substance use. The goal of this study is to develop and pilot test an intervention for families of YA-P who use cannabis to teach them skills to increase motivation among their YA-P to reduce their cannabis use. Relevant skills from motivational interviewing and the community reinforcement and family training interventions as well as psychoeducation centered on risks of cannabis to psychosis will be core elements of the intervention. Phase 1 will focus on the development of the Cannabis Conversation Skills for Families (CCSF) intervention material through the application of recently collected qualitative (focus group) data. Specific adaptations will include: the development of intervention content specific to YA-P such as education around the differential effects of THC potency on psychosis, and the impact of cannabis misuse on psychosis intervention outcomes. Materials will be iteratively adapted over the course of Phase 1 through pretesting the intervention with 10 families of YA-P who frequently use cannabis. Phase 2 will include the conduct of a randomized controlled pilot trial to assess feasibility, acceptability and preliminary effectiveness of the CCSF with 40 relatives of YA-P who frequently use cannabis and are engaged in coordinated specialty care. Participants will be randomly assigned to receive a 6- session group delivered CCSF or treatment as usual (TAU) intervention and will be assessed at baseline, and 3-month follow-up. The specific aims are: 1) develop the CCSF for relatives of heavy cannabis using YA-P; 2) conduct a 1-arm pretest (n = 10) and counselor training trial; and 3) assess the feasibility, acceptability and preliminary effectiveness of CCSF in a randomized pilot trial and assess target mechanisms of expressed emotion, caregiver burden and self-efficacy.