ABSTRACT: The objective of the present study was to evaluate the digestibility and the immunomodulatory effects of diets supplemented with lutein in dogs. Sixteen adult dogs were distributed in two groups (control and test) in a completely randomized design. Dogs were fed for 120 days with iso-nutritive diets, which only difference was the inclusion of 45g lutein/kg in the diet fed to the test group. Blood samples were collected in the beginning and at the end of the experimental period to evaluate total lymphocyte, lymphocyte proliferation index, and CD4+ and CD8+ lymphocyte counts. In order to evaluate apparent diet digestibility, dogs were housed in metabolic cages for ten days (five days of adaptation and five for faeces total collection). Coefficients of total tract apparent digestibility were not different between dogs in the control and the lutein-fed groups. Lutein dietary supplementation did not influence total lymphocyte or lymphocyte proliferation index, but resulted in higher CD4+ and CD8+ lymphocyte numbers. Lutein supplementation did not affect diet digestibility or lymphocyte proliferation index in dogs. However, it increases the concentrations of CD4+ and CD8+ T-lymphocyte subtypes.