Low levels of plasma vitamin E concentrations were found in canine atopic dermatitis (CAD). The present study was aimed at determining the effect of an eight-week vitamin E supplementation on clinical response (Canine Atopic Dermatitis Extent and Severity Index (CADESI-03) scores and pruritus intensity) in dogs with atopic dermatitis. Levels of oxidative stress markers (plasma malondialdehyde and total antioxidant capacity (TAC), blood glutathione peroxidase and erythrocyte superoxide dismutase, plasma and skin vitamin E concentrations) were also determined. Twenty-nine dogs with CAD were included in the study. Fourteen received vitamin E (8.1 IU/kg once daily, orally) and 15 received mineral oil as placebo (orally). All dogs were treated with antihistamine fexofenadine. Levels of oxidative stress markers (with the exception of skin vitamin E), CADESI-03 and pruritus intensity were determined at the beginning, then every two weeks. Skin vitamin E was determined at the beginning and at the end of the treatment. Significantly higher plasma levels of vitamin E and TAC were observed in the vitamin E group than in the placebo group. CADESI-03 scores determined throughout the treatment in the vitamin E group were significantly lower than in the placebo group. The findings of this study support the supplementation of vitamin E in dogs with atopic dermatitis.