Introduction: Use of chemotherapy for muscle-invasive bladder cancer (MIBC) is known to be low. To understand factors driving practice we use the Theoretical Domains Framework (TDF) to identify barriers and enablers of chemotherapy use. Methods: A convenience sample of Canadian urologists, medical oncologists (MOs), and radiation oncologists (ROs) participated in individual, semi-structured, one-hour telephone interviews. An interview guide was developed using the TDF to assess potential barriers and enablers of chemotherapy use. Interviews were recorded and transcribed. Two investigators independently identified barriers and enablers and assigned them to specific themes. Participant recruitment continued until saturation. Results: A total of 71 physicians were invited to participate and 34 (48%) agreed to be interviewed: 13 urologists, 10 MOs, and 11 ROs. We identified the following barriers to the use of chemotherapy (relevant TDF domains in parentheses): 1) belief that the benefits of chemotherapy are not clinically important (beliefs about consequences); 2) inadequate multidisciplinary collaboration (environmental context and resources); 3) absence of "champions" advocating the use of chemotherapy (social and professional role); and 4) a lack of organizational clarity/policy regarding the referral process (environmental context and resources). The predominant enablers identified included: 1) "champions" who believe in the value of chemotherapy (social and professional role); 2) urologists who refer all patients to MO (behavioural regulation; memory, attention, and decision-making); and 3) system-level factors, including automatic multidisciplinary referral (environmental context and resources). Conclusions: We have identified several system-level factors associated with delivery of chemotherapy. Behaviour change interventions should optimize multidisciplinary care of patients with MIBC. Patient summary: Despite the fact that chemotherapy before or after surgery improves survival of patients with bladder cancer, several studies have shown that many patients in routine practice are not treated. In this study, we identify important system-level and physician-level factors that must be considered in efforts to improve patient care.