Our recent pilot study showed better outcomes using a combination of low-dose cyclosporine and glucosamine than cyclosporine alone in the treatment of atopic dermatitis (AD). Here, a randomized, placebo-controlled, double-blind, parallel-designed study was planned to compare the efficacy and safety of low-dose cyclosporine and glucosamine combination to low-dose cyclosporine alone for the treatment of patients with moderate to severe AD. AD patients with a Severity Scoring of Atopic Dermatitis (SCORAD) index ≥30 were randomly assigned in a 1:1 ratio to receive either cyclosporine 2 mg/kg and glucosamine 25 mg/kg (group A) or cyclosporine and placebo (group B) for 8 weeks. SCORAD indices, serum levels of chemokine ligand 17 and interleukin-31, eosinophil counts, and blood cyclosporine levels were examined before and after treatment. The SCORAD indices for group A (n = 19) were significantly reduced after the treatment and a significant correlation between the changes in the SCORAD indices and changes in the serum levels of chemokine ligand 17, but not interleukin-31, was detected. Glucosamine combined with cyclosporine did not increase adverse events and serum cyclosporine levels compared with cyclosporine alone. Therefore, combination of low-dose cyclosporine and glucosamine may be useful to allow the long-term use of cyclosporine in the treatment of patients with moderate to severe AD.