Respiratory system plays a crucial role in sustaining important physical functions; thus, the control of the respiratory system is the first aspect in good intensive care unit patient care. Respiratory care consists of preserving the patency of the airways, oxygen treatment, respiratory monitoring, dental care, and care linked to preventing ventilator-associated infections. To evaluate the knowledge of critical care nurses toward educational program focus on oxygen therapy for coronavirus disease 19. A quasi-experimental design selected as suitable method to evaluate of effectiveness educational program toward COVID 19 patient's oxygen therapy on nurse's knowledge during the period of 3ed January 2022 to 26th February-2022. The study conducted at the critical care units which distributed at Al-Hillah Teaching Hospitals. Non-probability (purposive) sample selected, the original sample were divided to two groups, the first one is control group consist of (30) nurses, while the remining number (32) assigned as interventional group member. Proper questionnaire prepared for data collection. Most of participants in both groups 15 (48.4%), 15 (50%) were between (24-26) years age group, 19 (61.3%), 15 (50%) were male, 16 (51.6%) were diploma degree holder in interventional group, while 20 (66.7%) were bachelor degree in the control group, significant improvement in nurse's knowledge regarding oxygen supplement after their attendance to the educational program session, while the results shows no significant change for control group is presented in the following two post-test. Significant differences of interventional group between their pretest and two posttest recording for the nursing knowledge regarding oxygen therapy for coronavirus disease 19 patients, while no significant differences recorded among control group members.