Background: The present study aimed to compare the diagnostic efficacy of dynamic ultrasound and MRI in detection of full and partial thickness rotator cuff tears and to find out whether MRI can be replaced by dynamic USG in the diagnosis of rotator cuff injuries of shoulder. Methods: The study comprised of 116 patients who were clinically suspected to have rotator cuff tears. Sensitivity, specificity, positive and negative predictive values, accuracy and kappa values were calculated for both imaging modalities, with arthroscopic findings as the comparative standard of reference. Results: The sensitivity, specificity and diagnostic accuracy of dynamic USG for full and partial thickness rotator cuff tear were 97.1%, 95.7%, 96.6% and 97.8%, 92.9%, 94.8% respectively and the corresponding values for MRI for full and partial thickness rotator cuff tears were 98.6%, 97.8%, 98.3% and 93.5%, 97%, 96% respectively. There is almost perfect agreement between USG, MRI and arthroscopic findings in the detection of partial and full thickness rotator cuff tear as suggested by kappa value of more than 0.81. Conclusion: Dynamic ultrasonography and MRI have comparable degrees of accuracy for diagnosing rotator cuff tears. The use of dynamic ultrasound study, providing comparable information as that of MRI but less expensive, is therefore recommended for the diagnosis of rotator cuff disorders.