The effects on milk, butter and hard cooked cheese of new n-3 fatty acid (FA) sources in cows' corn silage-based diets – microalgae DHA Gold® (ALG), sieved extruded linseed (SEL) and their combination (SEL/ALG) – were assessed. Butter processing from ALG and SEL/ALG cream was not possible. Butter from SEL had less yellow colour and tended to be softer, with less rancid flavour and odour but stronger cream flavour. For SEL/ALG, cheese yield before brining was higher, but fat content in dry matter and curd dry matter were lower. For ALG and SEL/ALG, cheeses were evaluated as less coloured, more open, less firm, less elastic, more grainy and spicy. Cheese volatile compounds were affected by cows’ diet; higher concentrations of compounds from FA oxidation and amino acid catabolism were observed with the addition of microalgae DHA Gold®. Flavour profiles of cheeses were slightly affected by this addition, but no off-flavour was perceived.