Primary hyperlipidaemia in Schnauzer is characterized by increased plasma triglycerides (TG) and/or total cholesterol (TC) concentration and is associated with an increased risk of developing pancreatitis, insulin resistance and seizures. In humans, omega-3 fatty acids in addition to a low-fat diet can be used to reduce TG and TC. This study evaluated the therapeutic efficacy of omega-3 fatty acids associated to a diet management with two different fat content in Schnauzer with primary hyperlipidaemia. Eighteen dogs with primary hyperlipidaemia were divided into two groups: group 1, n = 10, 8 females, 2 males, age (mean ± standard deviation) of 7.13 ± 2.70 years and body weight (BW) (mean ± standard deviation) of 7.25 ± 1.22 kg were treated with fish oil (approximately 730 mg/day of omega-3) associated with a low-fat and low-calorie diet (approximately 24g of fat/1000 kcal) for 90 days (T90); and group 2, n = 8 dogs, 6 females, 2 males, with 7.0 ± 1.77 years old and average BW of 8.36 ± 1.51 kg, treated with fish oil (approximately 730 mg/day of omega-3) and maintenance diet with moderate amount of fat (approximately 33g of fat/1000 kcal) for 90 days. Plasma TG and TC concentrations and lipoprotein (LP) profile (VLDL, LDL, HDL) were evaluated before and after treatment. TG and TC serum concentrations, expressed in mg/dL (mean ± standard deviation), before and after treatment in group 1 were: TG = 391.30 ± 487.86 (T0) and 118.7 ± 135.21 (T90); TC = 308.2 ± 63.06 (T0) and 139 ± 36.91 (T90). As for group 2, TG = 391.63 ± 336.89 (T0) and 250.75 ± 211.56 (T90); TC = 257.25 ± 92.88 (T0) and 207.25 ± 63.79 (T90). A reduction (p<0.05) of TG and TC was observed in both groups. The distribution of TG and TC among LP was not different between the pre (T0) and post treatment (T90) periods. After 90 days of treatment, the administration of omega-3 fatty acids, associated with a low-fat or maintenance diet reduced triglyceridemia and cholesterolemia without altering LP profile. The current investigation shows that both therapies were effective in reducing plasma TC and TG concentrations without altering LP profile.