Purpose: Canine ehrlichiosis is an important tick-borne disease of dogs worldwide. In the present study, we aimed to determine the serum total antioxidant capacity (TAC), malondialdehyde (MDA), nitric oxide (NO), superoxide dismutase, (SOD), glutathione peroxidase (GSH-Px), adenosine deaminase (ADA) activity and serum protein profiles in dogs affected with naturally acquired ehrlichiosis. Methods: The animal materials had been consisted of ten dogs naturally infected with Ehrlichia canis, and ten controls negative for Ehrlichia canis. TAC, MDA, NO, SOD, GSH-Px, ADA activity and TP, ALB, GLOB levels were measured in sera of the animals. The serum protein concentrations were measured by autoanalyzer. The electrophoretic profiles of serum total protein were determined by native polyacrylamide gel electrophoresis (Native-PAGE). Results: In dogs with ehrlichiosis, decreased TAC (P < 0.05) and GSH-Px (P > 0.05) levels were determined. However, NO (P > 0.05), SOD (P < 0.05), ADA (P > 0.05), MDA (P > 0.05), TP (P < 0.05) and GLO (P < 0.05) levels were found as increased in the Ehrlichia positive dogs. ALB levels were decreased without a statistical significance (P > 0.05). ALB, α1 and β2 globulin strip densities were found as decreased in native-PAGE, while β1 and γ globulin strip densities were significantly increased in the E. canis positive group when compared to the control. Conclusion: It was determined that the oxidative stress decreased high antioxidant activity in dogs naturally infected with E. canis, and consequently, pro-oxidant and antioxidant defense and serum protein profiles were affected. It was thought that antioxidant supplementation could be beneficial to the treatment of the disease.