A case of geyser sign with acromioclavicular (AC) joint cyst with underlying rotator cuff tear is presented. Ultrasound modality is used to diagnose the clinical case of the AC cyst with positive geyser sign. A 91-year-old male patient presented with a complaint of right-sided shoulder and neck pain. The physical examination revealed a large lump on his right shoulder with restricted shoulder movements. During ultrasound examination, a chronic supraspinatus tendon (ST) tear and AC joint cyst with a positive geyser sign was observed. The ultrasound diagnosis was also confirmed with magnetic resonance imaging (MRI). AC joint cyst with geyser sign is a rare condition. Few cases have been published with this type of pathology. To our knowledge, this is the first report of its kind from Pakistani population.