In the context of rapid development of clinical pharmacy in China, therapeutic drug monitoring (TDM) has become a vital tool for rational medication and is widely concerned. TDM combines the knowledge of pharmacokinetic and pharmacodynamic to optimize individualized drug therapy, which can ensure drug efficacy, avoid excessive accumulation of drug, and reduce drug-drug interaction. Drug therapy in elderly patients is often accompanied by age-related changes in the processes of drug absorption, distribution, metabolism and elimination. The pharmacokinetic and pharmacodynamic behaviors of elderly patients differ significantly from those of normal adult population, which may lead to treatment failure or drug toxicity. TDM allows clinician to optimize dose and provides the most viable approach to individualize therapy. By researching the published literature, it is found that little data are available with respect to the special effect of TDM in elderly patients. Herein, focusing on elderly patients, we summarize types of commonly monitored drugs, therapeutic windows, and track the tends and opportunities of TDM. The purpose of this paper is to call for more attention to TDM in elderly patients. TDM should be implemented for the elderly to overcome age-related differences between dose and plasma concentration, to monitor possible drug-drug interaction, and to guide dose adjustment.