Background & Objectives: Today, medication errors has important role in reducing patient health and rising health care costs. Aim of this study was to evaluate frequency of medication errors and factors influencing the failure to report of medical errors. Methods: This study were cross-sectional and conducted in 2012, nurses community in Qazvin teaching hospitals were studied. A sample of 24 nurses selected according to the formula of the sample size and Survey instruments and consisted of three parts: Demographic information, Types of medication errors and barriers to reporting medication errors .Test-Retest test was equal to 86%. Results: The average age of nurses participating in this study was 31 years old and the average work experience of nurses was 7.89 years. Most errors related to infusion rate and drug sensitivity with an average error of 2.20 and 1.92 respectively. The lowest frequency was errors of prescription with mean of 1.28. The highest value of the reporting was process barriers with 2.78 and Average minimum amount of administrative barriers with 2.22. Conclusion: The role of nurses is crucial to prevent medication errors.Managers have to provide educational programs for teaching to nurses and notifying them of the importance of correct medication reports.