Objective: Anxiety and substance use disorders are highly comorbid and mutually maintain each other. Treatments for anxiety disorders that are well integrated into substance use disorder treatment have the potential to improve both anxiety and substance use outcomes. Method: Ninety-seven individuals seeking treatment at a community-based, evidence-based intensive outpatient program for substance use disorders who also had anxiety disorders were randomized to either (a) usual care (UC) at the intensive outpatient program; or (b) UC + coordinated anxiety learning and management for addiction recovery centers (CALM ARC), a 7-session, group-based, computer-assisted but therapist-directed treatment for anxiety disorders adapted for individuals with anxiety disorder and substance use disorder comorbidity. Results: CALM ARC + UC outperformed UC on measures of anxiety and substance use at posttreatment and at a 6-month follow-up. Conclusions: Adding CALM ARC to UC for patients with comorbid anxiety disorders and substance use disorders is superior to UC alone. Implications for future research and clinical practice are discussed.