Patients with comorbid bipolar and substance use disorders are at particularly high risk for treatment nonadherence and a host of negative consequences. However, no previous interventions have been designed specifically to address this problem. In the current study, we describe the rationale for and initial development of an adjunctive psychosocial intervention that targets adherence in patients with bipolar disorder who are substance abusers. The intervention involves brief in-person sessions and follow-up phone contacts with the patient and a significant other/family member. We describe the effects of this novel intervention on adherence and other psychiatric outcomes in a series of cases treated as part of our initial development work. Results suggest that the intervention is feasible and acceptable to patients and could be helpful in enhancing the effects of existing treatments. Given these promising results, we plan to test the intervention further in a randomized clinical trial.