Low back pain is a significant problem worldwide affecting 1 in 5 adults. Exercise-based physiotherapy has been shown to be an effective treatment; however, adherence is a major challenge in this population. Using Self-Determination Theory (SDT) as a guiding framework, this study examined physiotherapists’ perspectives on factors affecting, and strategies to improve, adherence to exercise-based rehabilitation among those living with low back pain. Six semi-structured interviews with practicing physiotherapists explored the role autonomy, social relatedness, and competence play in rehabilitation. Reflexive thematic analysis revealed 338 meaning units mapping onto 34 codes under 14 main themes. Participants highlighted that autonomy, competence, and social relatedness were all important factors influencing patient adherence. In terms of strategies to improve adherence, autonomy was targeted by providing patients with choice relating to what exercises they did and when they completed them, while competence was addressed by making sure patients understood their exercises. Specific to social relatedness, it was highlighted that the rapport between providers and patients was key in promoting adherence. Further, participants agreed that while valuable, group exercise in a clinical setting is difficult to achieve. Participants reported that if strategies were effective, patients moved from introjected to identified regulatory states during the rehabilitation process. These findings suggest that SDT provides an effective framework for (a) understanding strategies clinical physiotherapists use to improve adherence to exercise-based rehabilitation among low back pain patients and (b) in shaping future rehabilitation interventions within this patient population.