BackgroundIntegrative oncology (IO) appears to be beneficial to patients with cancer, but its implementation remains a challenge. Guided by the Theoretical Domains Framework (TDF) and the Capability-Opportunity-Motivation-Behaviour (COM-B) model, this systematic review identified the barriers to and facilitators of IO implementation in conventional cancer care settings. MethodsWe searched eight electronic databases from their inception until February 2022 for qualitative, quantitative or mixed-methods empirical studies reporting the implementation outcomes for IO services. Critical appraisal approach was tailored according to study types. The identified implementation barriers and facilitators were mapped onto TDF domains and the COM-B model, and subsequently onto the behavioural change wheel (BCW) for formulating behavioural change interventions. ResultsWe included 28 studies (11 qualitative, 6 quantitative, 9 mixed-methods and 2 Delphi studies) of satisfied methodological quality. The main implementation barriers were the lack of IO knowledge, the absence of funding and healthcare professionals low level of IO receptiveness. The key implementation facilitators were the dissemination of evidence on IO clinical benefits, the equipping of professionals with IO service delivery skills and the provision of a supportive organisational climate. ConclusionMultifaceted implementation strategies are needed to address the determinants influencing IO service delivery. Based on our BCW-based analysis of the included studies, the key behavioural change techniques are: (1) educating healthcare professionals about the value and application of traditional and complementary medicine; (2) ensuring access to actionable clinical evidence on IO effectiveness and safety and (3) designing guidelines on communicating traditional and complementary medicine interventions with patients and caregivers for biomedically trained doctors and nurses.