Therapeutic drug monitoring (TDM) of cancer drugs has been shown to improve treatment effectiveness and safety. The aim of this paper was to comprehensively review economic evaluations of TDM interventions for cancer drugs. Searches were conducted in four electronic databases, Medline, EMBASE, and Centre for Reviews and Dissemination (CRD) databases’ Database of Abstracts of Reviews of Effects (DARE) and the NHS Economic Evaluation Database (NHS EED), from their inception to June 2019. Studies were included if they were economic evaluations of TDM interventions for an active cancer treatment. The quality of reporting of economic evaluations was assessed using the Consolidated Health Economic Evaluation Reporting Standards (CHEERS checklist). Of the 11 publications identified, imatinib with TDM and 5­fluorouracil (5‐FU) with TDM were the most commonly assessed interventions (4 publications each). Overall Study quality was good, with publications meeting 61% to 91% (median 80%) of CHEERS checklist criteria. A variety of studies were used to estimate the clinical effectiveness inputs for the cost effectiveness models. All publications considered TDM to be cost‐effective based on an ICER below the WTP threshold (64%) or being cost‐saving (36%). TDM interventions were considered cost‐effective across the economic evaluations. Further clinical research assessing the impact of TDM on overall survival or other long‐term health outcomes may enhance the evidence base for TDM in oncology. Future economic evaluations of TDM should explicitly consider uncertainty in the underlying clinical evidence and incorporate changes in the use of newer targeted drugs that form the current standard of care.