Background: Adhesive capsulitis occurs with synovial inflammation and capsular fibrosis in the glenohumeral joint, leading to restriction of joint motion and pain. Heat therapy modalities, which aim at modifying dense collagenous tissues are commonly practiced interventions for patients with adhesive capsulitis; however, the effectiveness of ultrasound deep heat therapy (UST) on adhesive capsulitis is still unclear. Purpose: This systematic review and meta-analysis study was conducted to evaluate the effects of UST on the improvement of pain and glenohumeral joint function in adhesive capsulitis compared to (1) no treatment or placebo, and (2) any other therapeutic modalities. Methods: A literature search was carried out in January 2021 in Cochrane Central Register of Controlled Trials, PubMed, EMBASE, PEDro, Web of Science, and Google Scholar. The main outcomes of interest were self-reported pain scores, disability scores, and the range of motion. This study was conducted based on the guidelines of the PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analyses) protocols, using random-effects models. Results: Seven studies were included in the systematic review with five studies forming the basis for meta-analyses. The effects of UST in patients with adhesive capsulitis were compared with placebo, shockwave therapy, corticosteroid injection, platelet-rich plasma injection, or cryotherapy. The results indicated that UST significantly improved pain scores when performed together with exercise and/or other physical modalities compared to placebo; however, whether UST provides benefits for the improvement of disability and/or the range of motion was uncertain in the present results. Conclusions: The present findings suggest that UST as a co-intervention combined with other physical modalities is an effective means of improving the overall pain in patients with adhesive capsulitis.