The transition phase, typically defined as 3 wk before to 3 wk after parturition, is viewed as a critical time in the lactation cycle of a dairy cow. During early lactation dry matter intake (DMI) lags behind the nutrient requirements for milk yield. So, the onset of lactation in the dairy cow is characterized by a dramatic increase in the nutrient demands for milk synthesis. Fish meal (FM) is used in dairy cow ration as a source of RUP in some countries. Greater rumen escape of FM protein is known to increase efficiency of protein utilization in lactating cows. Moreover, FM has an excellent profile of amino acids and is a good source for the 2 most limiting amino acids for milk synthesis, lysine and methionine. Fish meal also contains oil (8 – 10% of DM) with relatively high concentrations of two polyunsaturated fatty acids (PUFA) of the n-3 family, eicosapentaenoic acid (EPA, C20:5) and docosahexaenoic acid (DHA, C22:6), which can be supplied only by the diet because EPA and DHA cannot be synthesized de novo in mammalian systems. Of the available feedstuffs that are high in undegradable protein, fish meal often is effective in improving milk production. Meanwhile, reports on the effect of fish meal on blood metabolites in pre-and postpartum cows are rare and needs more investigation. The objective of this experiment was to compare diets with or without fish meal from transition period up to 35 days in milk (DIM) and their effects on blood metabolites in early lactation Iranian Holstein cows.