In this study, we aimed to explore patient perceptions of adherence to tuberculosis (TB) treatment and construct a theoretical model of treatment adherence behavior. We conducted semistructured interviews with 11 adherent patients from Tanzania whom we recruited by purposive sampling. The interview data were analyzed by content analysis. We found that the patient’s intention to adhere is the most important determinant of adherence behavior. This intention is preceded by the decision to seek biomedical health care, and based on knowledge and beliefs about TB treatment and the motivation to be cured. The intention to adhere helps patients to cope with perceived barriers to adherence, such as socioeconomic difficulties, and to create an adherence-enabling environment in which the presence of social support plays an important role. Our preliminary adherence behavior model should be validated in larger, nonadherent patient populations and evaluated for its applicability to the development of adherence-promoting strategies.