Background: Oxygen in human life is playing very important role and it is a drug which is used extremely universally and practiced by medical specialties in a large amount. Supplemental Oxygen is deliver for respiratory failure patients and its widely used in critical care areas. Objective: To assess the nurse’s knowledge, attitude and practice towards administration of oxygen therapy to the critical ill patients. Methodology: A descriptive cross-sectional research study design was used. Results: The study reported that the nurses have moderate knowledge were 78 (49.7%) and with positive attitude were 80(51.0%), The practice of nurses were poor 92(58.6%). Conclusion: The study concluded that the majority of nurses having moderate knowledge, positive attitude and poor practices regarding administration of oxygen therapy to the critical ill patients.