There is widespread agreement on the co-occurrence of substance use and mental health conditions and the related need to integrate behavioral health services to address these needs in concert. However, in the case of the treatment of opioid use disorders (OUD), there are considerable controversies about the role of behavioral therapies in medication assisted treatment (MAT, e.g., buprenorphine), the most widely available treatment for OUD. Drawing on California’s efforts to expand the capacity of MAT providers, I examine how providers and system-level stakeholders serving rural patients distinguish between their mental health and substance use. Providers reported that many rural patients were ambivalent to participate in counseling that was mandated to receive buprenorphine. Yet many described how the initiation of buprenorphine among patients experiencing addiction was needed to “work on” or “see” psychiatric conditions hidden below addiction. Finally, providers describe different systemic cultures between addiction and mental health care that contributed to challenges in understanding and providing co-occurring services. Despite the wide consensus on co-occurrence, disagreement in the evidence and the cultural and systemic separation between mental health and addiction demonstrate continued barriers to creating integrated care.