The relationship between medication attitudes and adherence as well as reliable measures of medication attitudes need further study. This study examined the psychometric properties of the Attitudes Toward Mood Stabilizers Questionnaire (AMSQ) in bipolar participants and the relationship between medication attitudes and adherence, measured by the self-reported Tablets Routine Questionnaire (TRQ). Inclusion criteria included mood stabilizer treatment and 20% or more medication nonadherence. Measures were given pretreatment and posttreatment. Average age was 47 years; majority were female (69%), African American (67%), and unmarried (53%). AMSQ's test-retest reliability was ρ = 0.73 (p < 0.001). AMSQ correlated with TRQ (rs = 0.20, p < 0.01) at baseline. Factor analysis identified three factors: positive/favorable attitudes, negative/critical attitudes, and unintentional nonadherence. Change in AMSQ across time correlated with change in TRQ. The AMSQ is valid psychometrically and is sensitive to change. Medication attitudes are related to adherence behavior. Interventions should include targeting specific domains of medication attitudes, such as illness knowledge.