Introduction: Achieving adherence to medications can be a serious challenge for patients affected by inflammatory bowel disease (IBD). Medical treatment is fundamental for inducing and maintaining remission, preventing flares and reducing the risk of colorectal cancer. Non-adherence may affect patients' quality of life resulting in unfavourable treatment outcomes, more hospitalizations and higher healthcare-related costs. Recognising and improving adherence is therefore a primary aim for the treatment of IBD.Areas covered: We critically discuss the current knowledge on medication non-adherence in adult patients affected by IBD, also mentioning a few issues concerning the paediatric and adolescent populations. In particular, we reviewed the literature focusing on the definition and detection of non-adherence, on its extent and on the possible non-modifiable and modifiable factors involved (patient-centred, therapy-related, disease-related and physician-related). Furthermore, we analysed the interventional studies performed so far. The literature review was conducted through PubMed addressing medication non-adherence in IBD, using the keywords adherence' and related terms and IBD, ulcerative colitis or Crohn's disease'.Expert commentary: Adherence to therapy for IBD is a complex yet fundamental issue that cannot be solved by addressing a single aspect only. Future studies should focus on patient-tailored and multidimensional interventions.