BackgroundShared decision-making is a central component of person-centred care and can be facilitated with the use of patient decision aids (PtDA). Barriers and facilitators to shared decision-making and PtDA use have been identified, yet integration of PtDAs into clinical care is limited. We sought to understand why, using the concepts of complexity science.MethodsWe conducted 60-minute in-depth interviews with patients with diabetes, primary care physicians, nurses and dietitians who had participated in a randomized controlled trial examining the impact of MyDiabetesPlan (an online goal-setting PtDA). Relying on a qualitative description approach, we used a semi-structured interview guide to explore participants’ experiences with using MyDiabetesPlan and how it was integrated into the clinical encounter and clinical care. Audiotapes were transcribed verbatim, then coded independently by two analysts.Findings17 interviews were conducted (5 physicians, 3 nurses, 2 dietitians, 7 patients). Two themes were developed: (1) MyDiabetesPlan appeared to empower patients by providing tailored patient-important information which engaged them in decision-making and self-care. Patients’ use of MyDiabetesPlan was however impacted by their competing medical conditions, other life priorities and socioeconomic context. (2) MyDiabetesPlan emphasized to clinicians a patient-centred approach that helped patients assume greater ownership for their care. Clinicians’ use of MyDiabetesPlan was impacted by pre-existing clinical tools/workplans, workflow, technical issues, clinic administrative logistics and support, and time. How clinicians adapted to these barriers influenced the degree to which MyDiabetesPlan was integrated into care.ConclusionsA complexity lens (that considers relationships between multiple components of a complex system) may yield additional insights to optimize integration of PtDA into clinical care. A complexity lens recognizes that shared decision-making does not occur in the vacuum of a clinical dyad (patient and clinician), and will enable us to develop a family of interventions that address the whole process, rather than individual components.Trial registrationClinicalTrials.gov NCT02379078.