Fructosamine and glycated hemoglobin (HbA1c) concentrations were measured simultaneously in 222 dogs (96 healthy and 126 sick dogs). The dogs were divided into 3 groups according to the glucose concentration: hypo, hyper and euglycaemic dogs. Serum fructosamine concentrations were measured by the reduction test with nitroblue tetrazolium. A turbidimetric inhibition immunoassay and specific polyclonal antibodies were used to evaluate glycated hemoglobin concentrations. A significant correlation was found between glucose concentration and either fructosamine (r = 0.63, p < 0.0001) or glycated hemoglobin (r = 0.82, p < 0.0001). The correlation was higher in hyperglycaemic dogs for fructosamine (r = 0.80, p < 0.0001) and in hypoglycaemic dogs for glycated hemoglobin (r = 0.91, p < 0.005). We found a significant correlation between serum fructosamine and glycated hemoglobin (r = 0.65, p < 0.0001 ) when all the dogs were studied. A significant correlation was observed between serum fructosamine and glycated hemoglobin only in hyperglycaemic dogs (r = 0.82, p < 0.0003). Thus, fructosamine and HbA1c may be considered for use in screening tests for diabetes mellitus in dogs and clinical tests for monitoring control and evaluation of the diabetic animal's response to treatment. The choice of the analytical assay depends on the characteristic and analytical opportunities of the laboratory, as well as the number of serum samples to be analysed.