Pigmented villonodular synovitis (PVNS) occurs most frequently in the knee and hand joints and is extremely rare in the shoulder joints. A 27-year-old women was admitted to our outpatient clinic with an abrupt-onset pain and limited range of motion of the left shoulder. On arthroscopic examination, localized PVNS surrounding the reactive synovitis in the posterior aspect of the subscapularis within the shoulder joint cavity. The mass was removed using a grasper and shaver. Symptomatic relief was achieved following surgical removal. In conclusion, although rare, localized PVNS of the shoulder joint should be kept in mind in patients with a sudden-onset shoulder joint subluxation and pseudoparalysis.