Background: More than two decades of research mounts clear demonstration that providing an integrated, concurrent delivery of mental health and substance abuse treatment to persons with co-occurring substance use and psychiatric illness (also known as ‘dual diagnosis’ [DD]) renders best outcomes; yet, most persons suffering from these disorders do not receive such integrated interventions and most community-based behavioral health agencies are not prepared to provide it. Aims: To investigate the dual use of COMPASS-EZ and DDCAT instruments to (1) evaluate the current dual diagnosis capability of a community-based behavioral health agency; and (2) to develop and implement evidence-based recommendations to increase the agency’s dual diagnosis capabilities. Methods: A quality improvement (QI) initiative utilizing dual instruments to assess 22 programmatic domains of care and address the co-occurring capabilities of a single addiction treatment center for pregnant and postpartum women. Results: With all conditions met, focused quality improvements developed in policy for clinical documentation (recordkeeping), discharge planning, and staff competency assessment yield a prospective increase in DD-capability scores for the following COMPASS-EZ domains and agency overall: Program Policies [4.33 to 5.00], Screening and Identification [4.00 to 4.33], Integrated Discharge/Transition Planning [4.00 to 5.00], Program Collaboration and Partnership [4.20 to 5.00], and General Staff Competencies and Training [3.50 to 4.67]; total agency DD-capability score returned a prospective increase of 4.50 to 4.77. Conclusions: Findings suggest that across domains of care, community behavioral health agencies can continue to increase critical capabilities for patients with dual diagnosis through policy development. The collective application of one or more independent instruments proves useful to guide and measure the efficacy of quality improvement efforts.