Background: Calcific shoulder tendinitis (CST) is characterized by hydroxyapatite crystals deposition in the rotator cuff tendons. Therapeutic exercises have been the mainstay of CST treatment, and evidence for therapeutic ultrasound (T-US) utilization and efficacy is lacking. Aim: This study aimed to determine whether 4500 J T-US combined with therapeutic exercises is superior to therapeutic exercises alone regarding calcification size reduction and symptom improvement in chronic symptomatic CST. Design: This is a double-blind, placebo-controlled study. Setting: This study was conducted at a University Department for Rheumatic Diseases and Rehabilitation of a University Hospital. Population: Patients with chronic CST were analyzed. Methods: After eligibility allocation, 46 patients with sonographically confirmed CST were divided into two groups (56 shoulders, 26 per group). Both groups performed the same therapeutic exercises for half an hour under physiotherapist supervision. In the treatment group T-US (4500 J, 10 minutes per session at a frequency of 1 MHz and an intensity of 1.5 W/cm2), and in the placebo group, sham T-US was applied for 4 weeks. Patients were assessed for: calcification size, shoulder pain, global health (GH), shoulder mobility (ROM), handgrip strength, Health Assessment Questionnaire Disability Index (HAQ-DI), Shoulder Pain and Disability Index (SPADI), and overall rehabilitation satisfaction. Results: All assessed variables improved in both groups. A significantly greater reduction in calcification size was recorded in the treatment group compared to placebo: -10.92% (IQR 4.61% to 19.38%) versus -5.04% (2.30% to 7.22%), P=0.008. There was a significantly greater decrease in HAQ-DI, reduction of VAS GH, and an increase in hand grip strength in the treatment group, while no significant differences were observed for other parameters between the groups. Conclusions: Our results showed that adding the 4500 J T-US to therapeutic exercises in chronic symptomatic CST therapy resulted in greater calcification size reduction immediately following the treatment, as well as hand grip strength, HAQ-DI, and VAS GH improvement. Clinical rehabilitation impact: 4500 J T-US combined with therapeutic exercises is more effective in reducing calcification size than therapeutic exercises alone in the treatment of chronic symptomatic CST.