BackgRound The report from the Institute of Medicine, "To Err is Human," estimated that about 44,000 and 98,000 patients die each year in the United States of America because of medication errors. [1] Chemotherapeutic drugs were the second-most common cause of fatal medication errors. [2] Due to the complexity of chemotherapy regimens, medication errors can occur at any point from prescribing to administration. [3] In particular, errors in multiple-dose administration can result in catastrophic reaction or death. [4] The reported frequency of medication errors among cancer patients varies between studies, within studies by setting (e.g., outpatient vs. inpatient), [5-7] and route of administration (e.g., oral, intravenous, or intrathecal). [8] Nevertheless, it is unclear whether these suggested within-study factors explain the observed variation in medication errors between studies. To the best of our knowledge, the frequency of chemotherapy medication errors in prescribing, preparation, dispensing, and drug administration phases has not been compared at the time of drafting this manuscript. The present study is aimed to perform systematic review of published literature regarding the frequency of chemotherapy errors among cancer patients during various phases of therapy, i.e., prescribing, preparation, dispensing, and administration. Methods Search strategy A systematic search of the literature was conducted in Medline/PubMed, Agency for Healthcare Research and Objective: To synthesize peer-reviewed knowledge on the frequency of different types of chemotherapy medication errors. Methods: The data were collected from studies published between January 1, 2000, and March 3, 2018, and are identified through online resources such as Medline/PubMed, PubMed Central, Agency for Healthcare Research, and Quality and the Cochrane Library. The manuscripts published in peer-reviewed scientific journals in English language were included in the study. Initially, 19,723 articles were retrieved and finally 11 were found to be eligible to include in the review and were assessed for quality. Error percentages were calculated from the ratio of error type (numerator) to sample size (denominator: medication orders or prescriptions). Results: Overall, the chemotherapy medication errors ranged from 0.004% to 41.6% among various studies. Chemotherapy medication errors ranged from 0.1% to 24.6% in prescribing, 0.40% to 0.50% in preparation, 0.03% in dispensing, and 0.02% to 0.10% in administering phases. Conclusion: Prescribing phase had the highest number of chemotherapy medication errors reported, and least was reported during dispensing phase. We also noticed a need for harmonization for reporting of medication errors.