Drug administration error in the hospital ward is an ever-present problem and an all-too-frequent occurrence. Such errors are often made by nurses who fail to follow relevant nursing standards. The aim of this article was to describe an adverse event of chemotherapy-related medication error that happened in an academic hospital located in central Taiwan. The authors and their colleagues used root cause analysis to survey the adverse event and to suggest ways to improve the accuracy of nurse chemotherapy medication administration. We investigated medication administration of chemotherapy made by nurses between February 24th and 26th, 2008, and found that a number of nurses failed to administer medication properly. Based on data analysis, root causes were identified as: (1) directed prescriptions were unclear, (2) chemotherapy medication administration lacked protocol guidance, (3) education was insufficient and (4) computer systems were inadequately designed. Based on a literature review and matrix analysis, the task force identified four major categories in which improvements were needed. These included: (1) prescription promotion, (2) protocol development and standardization, (3) education for healthcare practitioners and (4) improvement of computer systems. After improvements were put into practices, the accuracy of chemotherapy medication administration by nurses increased to 100%. We shared the promotion experience with clinical managers to analyze and avoid adverse events.