Background: Iatrogenesis is unintended injury result of medical management rather than the disease process among hospitalized geriatric patients. Geriatric nurses should have the necessary knowledge about these iatrogenic events. Aim: determine the relationship between iatrogenic events of hospitalized geriatric patients and nurses' knowledge. Settings: The study was done at the inpatient unit of the orthopedic surgeries and traumatology department of El Hadara University Hospital and the surgical department of the Main University Hospital which is affiliated to Alexandria Governorate, Egypt. Subject: 100 hospitalized geriatric patients and 80 nurses who give direct care to them were included. Tools: Five tools were used for data collection as follow; Hospitalized Geriatric Patients' Socio-demographic Data Structured Interview Schedule, Hospitalized Geriatric Patients' Medical Record, Iatrogenic Events of Geriatric Patients Appraisal Tool, Socio-demographic Data of Geriatric Patient's Nurse Questionnaire, and Nurses' Knowledge of Iatrogenic Events Questionnaire. Result: The most prevalent type of iatrogenic events among the study geriatric patients is iatrogenic events related to drug reaction with a mean percent score of 75.75±35.93. The study nurses who reported poor level of knowledge represented by 52.5% while fair level of knowledge reported by 36.3% and 11.3% reported good level of knowledge with a mean percent of 49.55 ± 18.11 Conclusion: Although there was no significant relation between the level of nurses' knowledge and total score of iatrogenic events among hospitalized geriatric patients, a significant relation was found between nurses' knowledge and nursing-related iatrogenic events. Recommendations: Develop training educational program for nurses who care for geriatric patients about iatrogenic events' management.