Giant left atrium is the end product of severe and prolonged pressure and volume overload, occurring during mitral insufficiency or stenosis. Current surgical methods for left atrial volume reduction may be classified into three categories; partial plication of inferior wall (para-annular, Mercedes plasty and triangular resection of inferior wall), partial plication of inferior and superior walls and partial heart auto-transplantation. The aim of this study was to compare the effect of left atrial plication in two groups of patients who had mitral valve replacement and had a giant left atrium. This study was a retrospective prospective, randomized, observational interventional study and included 50 patients, divided into two equal groups; group A (mitral valve replacement and left atrial plication) and group B (mitral valve replacement only). There was statistically significant difference between the 2 studied groups regarding the Left atrial diameter in the echo findings, there is statistically significant difference between the 2 studied groups in terms of the intra operative TOE, valve implant type and pacing wires used, there was statistically significant difference between the 2 studied groups in terms of 1month ECHO LAD and 6months ECHO LAD diameter. There was statistically significant difference between pre and post-operative rhythm, left atrial diameter, compression symptoms and LA thrombus among cases in group 1 but no statistically significant difference was detected in terms of rhythm, and Left atrial diameter in group 2. So, we concluded that LA reduction along with MVR has significant improvement in clinical outcome in terms of restoration of sinus rhythm, less thromboembolic complications and compression symptoms during long term follow up.