Introduction: Early diagnosis of critical congenital heart defects (CCHD) may be missed both during prenatal echocardiography and the short stay in the neonatal nursery, leading to circulatory collapse or death of the newborn before readmission to hospital. Pulse oximetry screening (POS) has been proposed as an effective, non-invasive, inexpensive tool allowing earlier diagnosis of critical congenital heart disease (CCHD). Objective: This study was conducted to find out the role of pulse oximetry as a screening tool for early detection of critical congenital heart disease in newborn. Methodology: This prospective study was conducted in department of Neonatology and department of Obstetrics __ampersandsignamp; Gynecology, Bangabandhu Sheikh Mujib Medical University, Shahbag, Dhaka, Bangladesh a tertiary care hospital over one year. All inborn and outborn newborns stayed in hospital within 24 hours of age were included in this study. After taking written informed consent from parents, a thorough history was taken by investigator. Then pulse oximeter was used in standard way to measure reading from arms and legs. Interpretation and follow-up by Echocardiogram was done in pre-designed criteria. Data were calculated manually. Results: During the study period a total of 1033 newborn babies were screened. Among screened newborn positive screening rate was found 16(1.5%) cases. Newborns with positive screening were advised to do echocardiographic evaluation. Echocarbiography was done in all 16 babies and 4 newborn babies were having critical congenital heart diseases. This present study found sensitivity, specificity, PPV and NPV of pulse oximetry screening 100%, 99.6%, 25% and 100% respectively. On echocardiography critical congenital heart diseases were double outlet right ventricle, tetralogy of fallot, pulmonary stenosis and d-TGA. Conclusion: The present study concluded that with this high sensitivity, specificity and negative predictive value Pulse oximetry is safe, feasible and maybe wont to screen for critical congenital heart condition. It would be an attainable noninvasive method to detect the congenial heart disease along with the physical examination in newborn.