Background: Nurse’s knowledge regarding medication error can affect by many factors such as personal cause (stress, exhaustion), predisposing factor (long working shift, busy environmental setting), lack of experience and knowledge about medication error. Objective: The aim of this study is to assess nurses’ knowledge regarding medication error. Materials and Methods: A descriptive-correlation study was conducted.108 nurses were recruited conveniently. Two sample t-test, analysis of variance analysis (ANOVA) and correlation were used to analyze the data by SPSS version 23. Result: The result showed that mean knowledge score regarding medication error was 18.74 (±4.75) out of 30 total score, which indicated moderate knowledge level. There were significant relationships between nurses’ knowledge regarding medication error with age (p = 0.005), service experience (p = 0.039), monthly income (p = 0.000) and level of education (p = 0.000). Nurses who were in more service experience, held B.Sc. in nursing and who were in high monthly income, they have moderate level of knowledge score regarding medication error. It also showed that, nurses who were in less service experience, held diploma in nursing and who were in low monthly income, they have low level of knowledge score regarding medication error. Conclusion: The knowledge is the matters toward safe administration of medication and most of the nurses strongly agree to continue education program for prevention of medication error. Intensive regular retraining programs should be held aiming to improve nurses’ pharmacological information, encourage to report medication errors, hospital should provide continuing education to reduce medication error especially; younger and diploma degree nurses and hospital managers should respond to errors in a positive ethical and logical manner in order to enhance patient safety.