Pain is the most severe in patients after open thoracic surgery. Patients undergoing surgery report slightly higher pain intensity than other surgery types. The aim of the study: is to evaluate the effect of immediate pain management on oxygenation levels among early extubated patients post-heart surgery. Subjects and Methods:Quasi-experimental design; a sample of 60 patients (male and female)divided equally into two groups; study group (n=30) and control group (n=30). Setting: cardiothoracic ICU and cardiothoracic department at the cardiothoracic hospital that belongs to Minia University Hospitals, Egypt. Tools: Three tools: I: Socio-demographic and medical Assessment, II: oxygenation level assessment and III: Numeric Pain Scale. Results: Mean age of study and control groups were (38.4±5.4) & (37.2±4.8) year respectively. (40%) from the study group suffered a myocardial infarction and did coronary angioplasty, (43.3%) of the control suffered coronary artery stenosis (33.3%) among them did coronary angioplasty. Related to the pain scale there was a significant difference between study and control groups at p-value <0.05. Also regarding oxygenation level which presented by a significant difference between both groups about breathing sound and arterial blood gases test at 1^st, 3^rd and 7^th day of the study, presented by p-value <0.05. Conclusion: This study concluded that pain management has a positive effect on a patient's oxygenation level which was presented in improving patients breathing sound and arterial blood gases which reflected on the patient's outcomes post-cardiac surgery. Recommendations: All cardiac surgery patients should receive pain management strategies before their operations and the pain management strategies should be included in the protocol of care for cardiothoracic patients.