Athletes are susceptible to rotator cuff injury as the result of chronic overuse caused by repetitive overhead throwing or a single traumatic event. The diagnosis starts with a thorough understanding of anatomy, which is used to interpret physical examination and diagnostic imaging findings. Caution must be used when interpreting these findings because special maneuvers intended to isolate specific structures about the shoulder are largely nonspecific; rotator cuff tears are found in asymptomatic shoulders and may not be the source of symptoms. After a diagnosis has been made, classification systems exist that may help the clinician formulate a treatment plan and set patient expectations. In summary, an appreciation of the subtleties of diagnosing rotator cuff injuries in athletes is the foundation of successful treatment and outcomes.