Background: Medical Errors (ME) are inevitable part of any health care system and pose a threat to patient safety. Objectives: To determine the prevalence, forms, consequences and the underlying factors of ME among nurses in the University Hospital of Benha and to detect the prevalence of reporting ME and causes of un-reporting. Material and Methods: This cross-sectional study was conducted up on 257 nurses. Data were collected during December 2017, using an English self-administered, anonymous questionnaire sheet. Results: 36.2% of the studied nurses committed ME, 48.4% of them committed errors more than once. The most frequent form was giving wrong dose of medications (35.5%). Tiredness due to excessive overtime work and inadequate training of the nurses were the mostly reported underlying factors (62.6% and 39.3% respectively). The prevalence of ME was significantly higher among junior nurses (P=0.029), those graduated from nursing school and technical institute of nursing than faculty of nursing (41.6%, 29.6% and 16.7% respectively) (P=0.017), among single, widowed and divorced nurses than married ones (81.2%, 60%, 50% and 32.5% respectively) (P