Background: Several therapeutic methods have been proposed for frozen shoulder syndrome. These include suprascapular nerve block, a simple and cost-effective technique that eliminates the need for nonsteroidal anti-inflammatory drug therapy. Methods: This was a clinical trial that included patients with unilateral shoulder joint stiffness. Patients were divided into three groups: those treated with isolated physiotherapy for 12 weeks (PT group), those treated with a single dose intra-articular injection of corticosteroid together with physiotherapy (IACI group), and those treated with a suprascapular nerve block performed with a single indirect injection of 8-mL lidocaine HCL 1% and 2 mL (80 mg) methylprednisolone acetate together with physiotherapy (SSNB group). The variables assessed were age, sex, side of involvement, dominant limb, presence of diabetes, physical examination findings including erythema, swelling, and muscle wasting; palpation and movement findings; shoulder pain and disability index (SPADI) score; and the visual analog scale (VAS) score pre-intervention and at 2-, 4-, 6-, and 12-week post-intervention. Results: Ninety-seven patients were included in this survey (34 cases in the PT group, 32 cases in the IACI group, and 31 cases in the SSNB group). Mean age was 48.55±11.06 years. Fifty-seven cases were female (58.8%) and 40 were male (41.2%). Sixty-eight patients had a history of diabetes (70.1%). VAS and SPADI scores and range of mototion degrees dramatically improved in all cases (p<0.001). Results were best in the SSNB group (p<0.001), and the IACI group showed better results than the PT group (p<0.001). Conclusions Suprascapular nerve block is an effective therapy with long-term pain relief and increased mobility of the shoulder joint in patients with adhesive capsulitis.