<p>Understanding the factors that influence the adoption and implementation of evidence-based practices (EBPs) is crucial for expanding access to high-quality treatments for serious mental illness (SMI). This study evaluated how provider characteristics and perceptions influence adoption and implementation outcomes of the Transdiagnostic Intervention for Sleep and Circadian Dysfunction (TSC) in community mental health centers (CMHCs). CMHC providers (<i>N</i> = 124) were trained to deliver TSC to CMHC patients diagnosed with SMI (<i>N</i> = 395). Providers completed measures on demographic and professional characteristics. Additionally, assessments conducted after providers completed TSC training and delivered TSC to a patient measured provider perceptions of TSC (i.e., treatment fit, willingness and confidence) and adoption and implementation outcomes (i.e., referrals, sessions delivered, and treatment completion). Providers reported highly positive perceptions of TSC. Providers’ education was associated with number of referrals and treatment completion. Additionally, provider perceptions of the TSC’s appropriateness and feasibility at post-training predicted later perception of treatment fit. Overall, findings suggest providers perceive TSC to be well-suited for CMHCs, where provider characteristics are diverse, which bodes well for sustainment and scalability in community settings. </p><p><b>Clinical Trial Registration</b>: This study was preregistered on clinicaltrials.gov (identifier: NCT04154631) on November 6, 2019. <a href="https://clinicaltrials.gov/study/NCT04154631">https://clinicaltrials.gov/study/NCT04154631</a>.</p>