The effects of linseed oil supplementation on milk production, milk composition, and n-6/n-3 ratio of dairy cow’s milk were studied. Twenty-four Holstein Friesian crossbred lactating dairy cows were assigned into a 2x2 Factorial arrangement. All cows were fed approximately 6 kg/d of 21% CP concentrate. Treatments were: 1) concentrate plus 300 g/d of palm oil (PO) together with ad libitum corn silage (CS); 2) concentrate plus 300 g/d of linseed oil (LSO) together with ad libitum CS; 3) concentrate plus 300 g/d of PO together with ad libitum fresh grass (FG); and 4) concentrate plus 300 g/d of LSO together with ad libitum FG. Supplementation with LSO had no effect on DMI, milk production and milk composition. Milk fat content was also not affected by LSO supplementation. However, the milk C18:3n3 percentage was increased while n-6/n-3 FA ratio was decreased by LSO supplementation. It was concluded that the milk FA composition can be altered by 300 g/d LSO supplementation with increasing concentrations of potentially health beneficial FA and decreasing concentrations of SFA. Finally, LSO supplemented with ad libitum FG lowed n-6/n-3 FA ratio in dairy cow’s milk.