Atrial fibrillation (AF) is one of the common adverse effects of cardiac surgery with an incidence of approximately 65%. The present study aimed to evaluate the value PA-TDI duration ability to predict post-operative AF. Data of 100 patients who was diagnosed with severe mitral regurge and was referred for mitral valve surgery. PA interval was measured using tissue Doppler as well as routine echocardiographic parameters. After surgery patients was monitored to detect any attacks of atrial fibrillation. According to occurrence of atrial fibrillation patients was divided to two groups and compared the two groups. PA-TDI interval duration in group I was significantly prolonged than in group II P-value <0.001. PA-TDI duration more than 151 ms had an accuracy of 66% in detecting AF episodes post- operatively with sensitivity equal to 65 and specificity 68%. Positive predictive value for PA-TDI interval more than 151 ms was 76% and negative predictive value of this interval was 53%. This study discovered that Pre-operative PA-TDI duration represent an independent predictor of POAF. PA-TDI is a simple parameter whose cost is low, is not a time-consuming parameter to be measured, and is available in many modern echocardiographic