Background: Recent decades showed steady increase in the number of cases referred for redo cardiac surgery, which are associated with increased risk of morbidity and mortality compared to the first-time operations. We aimed to investigate the risk factors for hospital mortality and morbidity in patients who underwent mitral valve replacements for previous mechanical mitral valve dysfunction. Methodolgy: sixty patients underwent the study from July 2011 till June 2013. Preoperative, operative, and postoperative data were analyzed and evaluated for risk factors affecting hospital mortality and morbidity. Results: The hospital mortality was 15%. New York Heart Association functional class, pulmonary hypertension, neurological event, total bypass time, cross clamp time and renal impairment are the most important risk factors for hospital mortality. These factors with hepatic dysfunction, overweight, left ventricular dysfunction and increased end systolic diameter > 3.9 cm are risk factors for postoperative hospital morbidities in patients undergoing redo mitral valve operation for prosthetic mechanical mitral valve dysfunction. Conclusion: Once significant valve dysfunction is first noted, re-operation should be undertaken to minimize operative risk to avoid mortality and post operative morbidities.