Introduction: Although anti-TNF therapy has changed the scenery of pediatric inflammatory bowel diseases (IBD) immensely, there are still patients with an unfortunate outcome. Approximately one third of patients that initially respond to anti-TNF therapy will lose that response over time and need treatment optimization. Loss of response (LOR) is a big concern in IBD management and especially among pediatric patients where treatment options are more limited than in adults. In children it is even more important to sustain response with minimal toxicity. Therapeutic drug monitoring (TDM) is proposed as a tool to reach this goal. Areas covered: This review focuses on the importance of TDM of anti-TNF and the role TDM has in clinical practice of pediatric IBD. Expert opinion: Although TDM is not yet widely used in pediatric IBD, the available literature suggests it to be a promising tool, especially in patients with LOR to anti-TNF. There is increasing evidence that also in children, higher anti-TNF drug levels are associated with sustained response, and likewise low or undetectable trough levels increase the likelihood of LOR. TDM-based treat to target strategies are being designed in adult studies, but more prospective studies also in pediatric IBD populations looking at the role of proactive testing are needed.