Aims <p>This study aimed to identify the behavioral determinants influencing the integration of physical activity into the care pathway of postmenopausal women with hormone receptor–positive breast cancer. It specifically addressed the following research question: What are the main barriers and facilitators, from both patient and healthcare professional perspectives, that influence the integration of physical activity into routine care?</p> Methods <p>This qualitative study was based on the Theoretical Domains Framework and the Capability, Opportunity, Motivation – Behavior (COM-B) model.</p> <p>Semi-structured interviews were conducted and the analysis was guided by these frameworks, complemented by inductive thematic analysis, to capture nuanced insights in this clinical context.</p> Results <p>Barriers for patients include misconceptions, fatigue and difficulties with autonomous PA practice, while healthcare professionals emphasize the need for practical training and clear protocols. Key enablers included early physical activity assessment, personalized and playful interventions, peer support, and the emerging role of advanced practice nurses in structuring care transitions. Digital tools show promise for sustainable engagement when co-designed with patients and integrated into therapeutic relationships.</p> Conclusion <p>The study identifies concrete levers for integrating physical activity into oncology care, combining behavioral frameworks with nursing science to better understand clinical realities. These findings provide practical guidance for developing sustainable strategies and reinforce the need for person-centered, coordinated approaches to make physical activity a fully recognized component of breast cancer care.</p>