Background: Adherence is a critical component of clinical intervention utility, but little is known about how cancer patients with depression, particularly low-income, ethnic minority patients, perceive adherence to and drop out from treatment. Aim: To explore low-income, minority cancer patient perspectives about not adhering or dropping out of depression treatment. Methods: A qualitative substudy was conducted within the Alleviating Depression among Patients with Cancer (ADAPt-C) study. The intervention was an individualized stepped care depression treatment program provided by a clinical social worker in collaboration with a study psychiatrist. Patients randomized to the intervention were offered antidepressant medication and/or 8–10 sessions of problem solving treatment talk therapy. In-depth telephone interviews were conducted with 20 patients who had dropped out of depression treatment, using a grounded theory qualitative methodological approach. Results: Enrolled intervention patients were predominately Latina, Spanish-speaking, and foreign born. Most patients (12/20) acknowledged they had dropped out of treatment for a variety of reasons, including dissatisfaction with treatment, poor patient-provider relations, logistical and financial barriers, cancer treatment commitments, and language barriers. However, other patients (8/20) denied they had dropped out of treatment and/or became confused about being labeled as a “dropout.” Conclusion: A substantial percentage of low-income, ethnic minority patients who drop out of treatment for depression appear not to realize they have dropped out of treatment. Improving treatment adherence requires explanation of what constitutes adherence and the consequences of failing to do so from the perspective of both patient and provider.