The incidence and prevalence of Crohn's disease are increasing causing a significant disease burden. Therapeutic drug monitoring (TDM) is advocated as a promising tool for personalized or individual-tailored therapy strategies and has been welcomed as a new means to improve current therapy strategies. Nevertheless, pharmacokinetic-based TDM has limitations, and straightforward target concentrations for most therapies are lacking. Areas covered: In the following concise review of literature, key insights of TDM in thiopurine, methotrexate, anti-TNF, vedolizumab and ustekinumab therapy for Crohn's disease are being described. Expert opinion: Therapeutic drug monitoring may, up till now, be helpful to adjust thiopurine and infliximab therapy, primarily in a reactive setting, in case of inefficacy and of occurrence of adverse event. With this restricted application, the goal of individualized therapy based on TDM has not yet been achieved.