Background/Objective: The management of patients with atopic dermatitis (AD) is often difficult for both patients and physicians. We hypothesized that repeated intramuscular injections of autologous immunoglobulin can induce clinical improvement in patients with AD by correcting immune dysfunction. Methods: Seventeen adult patients with severe AD were treated by intramuscular injection of 50 mg autologous immunoglobulin (mainly IgG with a purity ≥97%) twice a week for 4 weeks. The standardized clinical severity scoring system for AD (SCORAD) value and serum IgE concentration were measured at baseline and at 4, 8, and 12 weeks. Results: SCORAD values and serum IgE concentrations significantly decreased at 4, 8, and 12 weeks compared to baseline (p < 0.05). No significant side effects were observed. Conclusions: Repeated intramuscular injections of autologous immunoglobulin significantly decreased the clinical severity and serum IgE concentration in patients with severe AD. Further studies are required to evaluate the clinical significance of these findings.