Introduction: Application of the reach, effectiveness, adoption, implementation, and maintenance (RE-AIM) framework using mixed methods to evaluate a collaborative care practice implementation can inform the literature on real-world collaborative care experiences. Method: Two primary care practices serving Niagara Falls, NY, implemented collaborative care. Adults age 18 and over were screened at least annually for depression, anxiety, and alcohol use using the 9-item Patient Health Questionnaire (PHQ-9), the 7-item Generalized Anxiety Disorder questionnaire (GAD-7), and the AUDIT alcohol consumption questionnaire (AUDIT-C). Primary care clinicians referred patients screening positive to the on-site behavioral health care manager (BHCM) with warm handoffs; the BHCM used a mixed therapeutic approach, initiated consultations with a psychiatrist and a community resource liaison as needed, in collaboration with the clinician. External evaluators used mixed methods to assess collaborative care services’ RE-AIM. Results: Nearly 40% of patients screened positive for at least one behavioral healthcare (BH) concern or were referred to BH services upon clinician judgment. Of these patients, 43% were referred to integrated BH services, of whom 86% accepted and 54% actually participated in services. There were no differences in changes in symptoms between those who did and did not participate in services. Patients reported the services were valuable and helped build skills for coping with complex health conditions and psychosocial issues. Discussion: Evaluation of collaborative care using the RE-AIM framework may help others systematically evaluate programs, identify local improvement opportunities, and contribute to the broad literature on integrated care dissemination and implementation.