This study was conducted to determine the effects of orally administered borax on milk yield and on several blood variables related to metabolism in early lactation in Austrian Simmental cows (Fleckvieh). Twenty primiparous cows were selected at parturition and then assigned to one of two groups, the control group or the borax group. The study lasted for four weeks. Borax was administered orally at 0.2 mg/kg/day (Boron group) to all treatment cows shortly after the noon milking, whereas cows in the control group were not treated. All cows consumed the same diet. All feeds in the diet were analysed for crude cellulose, protein, ether extract, ash, and dry matter according to the Weende Analysis Systems, in addition to ADF and NDF, according to Van Soest. Blood samples were collected from all cows via the vena jugularis on lactation Days 0, 7, 15, 21 and 28 and analysed for the following: serum boron (B), non-esterified fatty acids (NEFA), beta-hydroxybutyric acid (BHBA), total cholesterol (TChol), high density lipids (HDL), total protein (TP), blood urea nitrogen (BUN), albumin (ALB), creatine (CRE), uric acid (UA), glucose (GLU), aspartate aminotransferase (AST), alanine aminotransferase (ALT) and gamma-glutamyl transpeptidase (GGT) concentrations. Serum B concentration was higher in the borax group than in the control group at Weeks 1, 2, 3, and 4 of the experiment. Serum B concentration did not change in the control group during these weeks, but it gradually increased in the borax group week by week (P < 0.05). Borax administration increased serum TP and decreased the serum UA concentration at Week 4, and decreased serum HDL concentration at Week 3 of the experiment. Serum TChol, BHBA, and BUN concentrations increased (P < 0.05), while NEFA decreased (P < 0.05) after parturition in both groups. The BHBA concentration gradually increased in the control group, but it began to decrease in the borax group during the final week of the experiment. Moreover, milk yield did not differ between the groups for 14 weeks. The results indicate that borax administration did not have any negative effects on the health of Austrian Simmental (Fleckvieh) cows during early lactation. However, studies of longer duration are needed to reveal the effectiveness of borax administration with respect to early lactation in cows.