Purpose: This study identified the individuals responsible for making decisions about physiotherapy (PT) wait time, frequency of treatment, and treatment duration for persons with low back pain and determined which factors guided these decisions. Method: A cross-sectional survey was sent to Canadian PT professionals treating adult patients with musculoskeletal problems. It included a clinical vignette describing a patient with low back pain. Respondents were asked who made decisions about wait time, treatment frequency, and treatment duration as well as on which factors they based these decisions. Results: Clinicians were most often responsible for making decisions about treatment frequency and duration. Although clinicians and managers or coordinators were mainly responsible for making decisions about wait time, there was more variability depending on sector of care: in the private sector, administrative assistants played a much larger role. Clinical judgment, clinical guidelines, and patients' demands were the predominant factors influencing wait time and frequency decisions. Treatment duration was related to patients' goals, clinical progression, patients' motivation, and patients' return to work. Conclusions: Decisions about service provision for wait times are made by a range of stakeholders, and a wide variety of factors guide Canadian PT professionals' decision making. Identifying these factors is essential for informing a discussion of decisions about evidence-based and equitable service delivery so that the actors involved can reach a consensus.