Background: Occupational exposures to blood and body fluids as a result of needle stick injuries is a serious concern for health care workers and a major risk for the transmission of infections such as human immune deficiency virus (HIV), Hepatitis viruses and other viral diseases among healthcare workers. Objective: To assess the prevalence of needle stick injuries among nurses and their immediate response at Tikur Anbessa Specialized Hospital, Addis Ababa, Ethiopia. Methods: A cross-sectional study was conducted in Tikur Anbessa Specialized Hospital from March to April, 2016. The sample size was calculated using single proportion formula and 313 nurses were included in the study. The sample size allocated proportionally to all nurses working in different departments and was selected using systematic random sampling technique. Data was collected using semi structured self administered questionnaires which consists of questions on socio-demographic characteristics, prevalence of needle stick injuries, its risk factors and action taken after injuries. Descriptive statistics were used to assess magnitude of needle stick injuries and immediate response. Multivariate logistic regression analysis was used to identify the factors associated with the outcome variable. Statistical significance set at P-value<0.05. Results: The life time needle stick injuries among nurses was 37.7% (95% CI: 32, 42.8) and the last one year prevalence was 14.1 % (95% CI: 10.4, 18.2). Forty six (15.5%) injuries occurred during intravenous injection, seventeen (5.7%) during intramuscular injection and twenty five (8.4%) during recapping of the needles. Thirty three (11.1%) of them washed the injured part with water and soap and applied antiseptics as immediate measure. Factors associated with needle stick injuries were recapping needle after use, working in emergency unit, and uncomfortable work environment. Conclusion: The prevalence of needle stick injury among nurses of Tikur Anbessa Specialized Hospital was high and the immediate action taken after the injury is not compliant to the universal precautions. Therefore, reporting to the concerned bodies, screening after needle stick injuries and promotion of a safety measures and universal precaution should greatly encouraged.