PURPOSE: This study was designed to investigate an accuracy of visual estimation of blood loss and the usefulness of simulation-based educational program for postpartum hemorrhage. METHODS: The participants included 12 nurses and 8 residents who were working at Mother and Baby Center of Ewha Womans University Hospital. A simulation-based education for estimation of blood loss was conducted for all of the participants. Tests were performed before and after simulation-based education. Two additional tests were performed two and four weeks after the education. Self-confidence score for blood loss estimation was also investigated by questionnaire. RESULTS: Significant underestimation was observed in all questions of 450, 700, and 1,100 mL. Median for percent errors of each questions were -50%, -29%, and -9%, respectively. After simulation-based education, accuracy was improved with the medians of -5%, 0%, and 13%. Selfconfidence score in visual estimation of blood loss was also improved significantly after the education. There were no differences by profession or work experience. CONCLUSION: Significant underestimation was seen before simulation-based education. This study shows that the accuracy of visual blood loss estimation was improved after education. Accurate estimation of blood loss will contribute to a timely diagnosis and resuscitation in postpartum hemorrhage. Our study suggests that periodic education for visual estimation of blood loss in obstetrical hemorrhage might improve accuracy and clinical outcome.