Aim: This study aims to evaluate the diagnostic accuracy of magnetic resonance (MR) imaging in detecting rotator cuff tears by correlating its findings with arthroscopy, the gold standard diagnostic tool. The study further investigates the agreement between these modalities in tear size measurement and tendon-specific detection rates. Materials and Methods: This prospective study included 110 participants aged 18–75 years with clinically suspected rotator cuff tears. All participants underwent MR imaging followed by arthroscopy within four weeks. MR imaging was conducted using standardized protocols, and findings were interpreted by blinded radiologists. Arthroscopy was performed by experienced orthopedic surgeons who documented tear characteristics and tendon involvement. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall accuracy were calculated, and interobserver agreement was assessed. Statistical analyses included p-value determination for all comparisons. Results: MR imaging showed high diagnostic accuracy for rotator cuff tears, with sensitivity, specificity, PPV, NPV, and overall accuracy of 84.2%, 88.6%, 86.7%, 87.1%, and 86.9%, respectively, for partial-thickness tears. For full-thickness tears, these metrics were higher, at 92.1%, 95.2%, 94.3%, 93.5%, and 93.8%, respectively (p = 0.04 and p = 0.03). Tear size measurements between MR imaging and arthroscopy demonstrated strong agreement (p < 0.001). MR imaging detection rates were highest for the supraspinatus tendon (89.1%), followed by the infraspinatus (87.4%) and subscapularis (83.7%) tendons. The teres minor tendon showed the lowest detection rate (78.4%). Conclusion: MR imaging is a reliable, non-invasive diagnostic tool for evaluating rotator cuff tears, particularly full-thickness tears and supraspinatus involvement. However, minor discrepancies in tear size and tendon-specific detection rates highlight the complementary role of arthroscopy in definitive diagnosis and surgical planning. Optimizing MR imaging protocols can further enhance diagnostic precision.