Objective: Frozen shoulder, a condition characterized by the limitation of active and passive shoulder movements, is predominantly man- aged conservatively. Corticosteroid injection stands as a widely utilized and effective method for treatment. Nevertheless, the optimal approach for administering the injection remains a subject of controversy. We hypothesized that the injection of corticosteroid through anterior into the extra-articular area would yield superior results than the posterior intra-articular injection. Methods: This prospective, randomized, single-blind, and single-center clinical study aimed to compare the therapeutic effectiveness of ultrasound (USG)-guided injection techniques in patients with primary frozen shoulder. We continued the study with 54 patients who met the inclusion criteria. We evaluated patients pre-injection and at the first, third, and sixth weeks after injection. Two distinct approaches were employed: (1) Injection through the anterior extra-articular area around the coracohumeral ligament (CHL), and (2) injection through the posterior route into the glenohumeral joint. Evaluation parameters, including Visual Analog Scale (VAS) scores, active range of motion (ROM), American Shoulder and Elbow Surgeons (ASES) scores, and Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH) scores, were assessed pre-injection and at the first, third, and sixth weeks post injection. Results: No significant differences in the demographic and clinical characteristics, laboratory, or radiological findings were observed between the groups. It was observed that both groups exhibited similar and significant improvement in all measured parameters within their respective groups. Regarding pain scores, a notable decrease in VAS scores was observed in both groups (P = .000). There was no difference between the groups in terms of pre-injection VAS, QuickDASH, and ASES scores and active ROM measurements. Conclusion: The study concluded that there was no significant difference between ultrasound-guided injection of posterior intra-articular injection and anterior extra-articular injection concerning pain, ROM, and functional scores. Both techniques can be considered as viable options in the early stage of the disease. Level of Evidence: Level I, Therapeutic study.