Background: Linseed (seed of flax) contains high amounts of ω-3 Fatty acids, which is said to have antihyperlipidemic effects. Materials and Methods: In this study, blood lipid levels (Triglycerids, Cholesterol, LDL, HDL) of 56 hyperlipidemic patients were measured before and after Linseed administration (6 gr linseed powder daily as a biscuit formulation for 3 months as a supplementation to their simple diet). The results were analysed by t-test using SPSS software. Results: There were some decreases in the mean level of serum total cholesterol (about 10% decrease, P=0.001), mean serum triglyceride (about 12% decrease, P=0.001), and mean serum LDL (about 10% decrease, P=0.001) before and after Linseed administration. The total-Cholesterol/HDL and LDL/HDL ratios decreased concordantly as well. However, there was no significant alteration in serum HDL level after linseed administration. Conclusion: Linseed administration combined with a simple diet, clinically decreases blood lipid levels. Hence, supplementation of simple diet with 6 gr Linseed powder daily, seems to be helpful in reducing patients blood lipid levels.