Abstract: An experiment was conducted by eight lactating Holstein cows with an average milk production of 32.75 kg day-1 and body weight of 643.6 kg to evaluate the effects of propylene glycol (PG) on productive performance, blood metabolites and nutrients digestibilities. In this experiment a balanced change-over design with four treatments and four periods with 21 days were employed. Treatments included: (1) Control (without PG), (2) 250 g PG/cow/day, (3) 500 g PG/cow/day and (4) 750 g PG/cow/day. Daily milk yield recorded and milk samples were taken during seven and two last days of each period. The results show that dry matter intake, milk yield, fat corrected milk yield, milk compositions were not affected (p>0.05) by different levels of PG. Supplementing diets with 500 and 750 g PG/cow/day, significantly increased plasma glucose (p<0.05) but other blood metabolites such as blood urea nitrogen, triglyceride and cholesterol were not affected (p>0.05) by PG. Apparent digestibility of dry matter and organic matte was not affected (p>0.05) by PG administration. In conclusion, plasma glucose was increased by using 500 and 750 g PG/cow/day (as powder) in the first and mid lactation stage, but the levels of 250 g PG/cow/day did not have any significant effect on dry matter intake, milk yield, milk compositions and other blood metabolites.