The effect of different levels of alfalfa hay and corn silage, in early lactation diet, on milk production and on milk components in Holstein cows was investigated. Fifteen Holstein cows (37 ±10 DIM) were taken in a completely randomized design experiment, lasting for 9 weeks. Three levels of hay and corn silage namely: 1) 10% alfalfa -30% silage corn (Diet 1), 2) 20% alfalfa -20% silage corn (Diet 2) and 3) 30% alfalfa -10% silage corn (Diet 3) former the treatments. The ratio of forage to concentrate was taken as the same (40: 60) in all the treatments. Cows were fed in Total Mixed Rations (TMR) and twice daily. They were milked 3 times a day at 02:00, 10:00, and 18:00 h. Milk production was recorded at each milking, but milk composition was weekly determined. Dry matter intake for each cow was daily assessed. Dry matter intake was higher (P<0.05) when cows fed diet 2 (23.20 kg per day) as compared with diets 1 (22.95 kg per day) and 3 (18.64 kg per day). Treatments affected milk production (P=0.014). Substituting corn silage with alfalfa hay increased the percentage of milk fat (P<0.05), but did not affect milk protein (P>0.05). Apparent total tract digestibility of dry matter (DM), organic matter, crude protein and neutral detergent fiber did not significantly differ among different dietary treatments (P>0.05). Blood parameters were not seriously affected by dietary treatments (P>0.05), although glucose content for Diet 1 was higher than that for Diet 2.