Dairy cows undergo an increase in metabolic processes during the transition period, leading them to be more susceptible to metabolic and oxidative stresses that are implicated in many periparturient diseases. Therefore, the neutralizing capacity of antioxidants plays an important role in reducing oxidative stress, particularly during the transition period. Accordingly, the objective of this study was to evaluate the effect of oral supplementation of dietary probiotic Bacillus subtilis (PROBS) on the overall antioxidant capacity in periparturient dairy cows. Twelve cows from a smallholder dairy farm were randomly assigned into 4 groups: a control group (CON), a group with a single intramuscular administration of 1,000 mg of α - tocopherol acetate (vitamin E) and 10 mg of selenium selenite on d 21 prepartum (ES), a group with daily oral supplementation with PROBS at 0.5 × 10¹¹ (BS0.5), and a 1.0 × 10¹¹ (BS1.0) colony - forming unit (cfu) during d 21 prepartum to d 14 postpartum. Blood samples were collected on days −14, 0, and 14 relative to the expected calving date for the serum total antioxidant status (TAS) measures of overall antioxidant capacity during the transition period. Repeated measure analysis was conducted to determine the effect of PROBS on TAS. Overall means and standard errors of the mean (SEM) of TAS on days −14, 0, and 14 were 1.77 ± 0.094, 1.72 ± 0.131, and 1.77 ± 0.107 mmol/L, respectively. Cows in BS0.5 (2.01 mmol/L) were the only group that had a trend for higher TAS than the CON (1.40 mmol/L). In conclusion, supplementation of dietary probiotic B. subtilis at 0.5 × 10¹¹ cfu/cow per day during 3 weeks prepartum to 2 weeks postpartum could be utilized as a beneficial feed additive with improved antioxidant capacity in dairy cows during the transition period.