Moderate-to-severe subacute thyroiditis is clinically managed with 6 to 8 weeks of glucocorticoid therapy. However, no studies have evaluated short-term prednisone treatment for subacute thyroiditis. This 24-week, prospective, single-blind, randomized controlled study enrolled patients (aged 18 to 70 years) with subacute thyroiditis who were hospitalized between August, 2013, and December, 2014. Patients with moderate-to-severe symptoms were randomly assigned to receive either 30 mg/day prednisone for 1 week, followed by 1 week of nonsteroidal anti-inflammatory drugs, or the conventional 6-week prednisone therapy. The primary endpoint was intergroup differences in treatment efficacy at the end of the treatment course. Secondary endpoints included between-group differences in post-withdrawal adverse effect parameters and thyroid function at weeks 6, 12, and 24. We screened 96 patients, randomized 52 participants, and 50 participants completed the study. Efficacy and recurrence rates were not significantly different at withdrawal in both groups (P = .65). At treatment discontinuation, parathyroid hormone (28.8 versus 38.9 pg/mL; P = .011) and systolic blood pressure (113.9 versus 122.4mm Hg; P = .023) were significantly lower in the experimental group than in the control group. There were no significant intergroup differences in other secondary endpoints at withdrawal and in thyroid function at weeks 6, 12, and 24. Fewer side effects of glucocorticoids and similar efficacy and recurrence rates were observed with short-term prednisone compared with the 6-week treatment for subacute thyroiditis. Short-term prednisone, with a better safety profile, may be an alternative strategy for ameliorating moderate-to-severe symptoms of subacute thyroiditis. BPPG = breakfast postprandial plasma glucose; CRP = C-reactive protein; ESR = erythrocyte sedimentation rate; FPG = fasting plasma glucose; FT3 = free triiodothyronine; FT4 = free thyroxine; GA = glycated albumin; NSAIDs = nonsteroidal anti-inflammatory drugs; OC = osteocalcin; PINP = type I procollagen amino-terminal peptide; PTH = parathyroid hormone; RCT = randomized controlled trial; SAT = subacute thyroiditis; SBP = systolic blood pressure; TC = total cholesterol; TSH = thyroid-stimulating hormone; TBG = thyroid-binding globulin; TG = triglyceride; TGAb = antithyroglobulin antibody; TPOAb = antithyroid peroxidase antibody; TRAb = antithyroid-stimulating hormone receptor antibody.