Background Despite developments in cognitive behavioural therapy for bipolar disorder, little is known about the specific dysfunctional beliefs that may predispose individuals to mania. Therefore a measure was specifically designed for this purpose based on a cognitive approach. The measure is called the Hypomanic Attitudes and Positive Predictions Inventory (HAPPI). Method Fifty-six individuals with a diagnosis of bipolar disorder and 39 matched healthy controls completed a brief version of the HAPPI (Brief-HAPPI), the Internal State Scale, and the Hypomanic Interpretations Questionnaire (HIQ). Results The bipolar group scored higher on the overall Brief-HAPPI scale, higher on the forward items of the Brief-HAPPI, lower on the reverse items and no different on the filler items. The group differences in overall score remained when controlling for current self-reported symptoms of mania and depression, and recent history of hypomanic symptoms, yet within the bipolar group, Brief-HAPPI score was positively correlated with the level of symptoms. The Brief-HAPPI showed a sizeable correlation with the HIQ, yet each scale showed a significant and independent association with bipolar disorder. Conclusion The Brief-HAPPI assesses dysfunctional beliefs that are associated with a diagnosis of bipolar disorder.