The objective of this study was to evaluate the effect of supplementing close-up diets with rumen undegradable protein on serum metabolites and the incidence of health disorders of Holstein dairy cows, during the hot season. Eighty-eight multiparous Holstein dairy cows were randomly assigned to 1 of 2 treatment groups: low crude protein (14.3% CP; 14CP) and high crude protein (17.1% CP; 17CP) diets. Blood samples were collected weekly from d -30 up to calving and then at 0, 5, 14, and 21 days after calving, for serum metabolites determination. Cows fed the 17CP diet had higher serum concentrations of albumin, blood urea nitogen, and Mg than 14CP cows during the close-up period. In postpartum, the 17CP cows had higher serum albumin and creatinine and lower free fatty acid, BHB, and glucose concentrations than the 14CP cows. The risk to developing subclinical ketosis (SCK), metritis and endometritis were higher for the 14CP cows than the 17CP cows. Overall, feeding high rumen undegradable protein diet to close-up cows during the hot season increased serum creatinine concentrations and lowered the incidence of SCK and metritis and endometritis postpartum.