This work aimed to investigate the effect of supplementing different forms of linseed (meal , whole linseed and oil) to lactating cow's ration on milk yield and milk composition. Sixteen multifarious Friesian cows 15±2.26kg milk /d, and averaging 460±15.26 kg/body weight, were divided into four experimental feeding groups (4 each) for 180 days. All group animals were received concentrate feed mixture containing zero, linseed meal, whole linseed and oil linseed in ration A, B, C and D, respectively. All experimental rations  were almost equals in energy and protein. Results indicated that supplementation of linseed meal recorded the highest FCM (13.60 kg/h./d.). There were no significant differences in milk composition among groups. Supplementation linseed oil (D) reduced the apparent digestibility of CF compared with control. The different form of oil seed did not influence ruminal pH but it caused significant (P<0.05) increased in ruminal ammonia concentrations for (C) and (D) groups compared with control. While, the concentration of volatile fatty acids was significantly (P<0.05) differ for cows fed (B) and (D) except those fed rations  (C) compared with control . From the previous results, it could be concluded that using linseeds, especially meal, in lactating cow's rations increased milk yield decreased feed cost and give more profit per Kg milk without adverse effects on cow's health or performance.