Recent studies have shown that probiotic supplementation during late gestation exerts some beneficial effects on reproductive performance of the sows. This study aimed to investigate effects of Bacillus subtilis QST 713 supplementation in gilts on different reproductive criteria. A total of 94 Camborough-48 gilts at day 85 of gestation were randomly allocated into 2 groups: (1) control diet; (2) control diet + 4 × 10 8 CFU Bacillus subtilis QST 713 per day. Gilts were supplemented until farrowing. At farrowing, litter size, number of piglets born alive, stillbirths, mummies, birth weight, farrowing duration, and birth interval were recorded. Within litter variation of piglet birth weight, depicted as SDBW and CVBW, was also calculated. Results showed that Bacillus subtilis QST 713 supplementation decreased stillbirth rate (1.26 vs. 4.37%, p=0.035) and increased birth weight of the piglets (1303.94 vs. 1234.09 g, p=0.007). Also, the litter size (11.85 vs. 10.67, p=0.03), number of piglets born alive (11.71 vs. 10.23, p=0.008), and litter weight (15473.06 vs. 13174.86 g, p=0.002) in the treatment group were higher than those in the control. Farrowing duration (174.39 vs. 160.81 minutes, p=0.162), birth interval (16.32 vs. 16.59 minutes, p=0.674), SDBW (85.07 vs. 94.65 g, p=0.343), and CVBW (6.42 vs. 7.85, p=0.12) were independent of the Bacillus subtilis QST 713 supplementation. Results of the present study indicate that supplementation of Bacillus subtilis QST 713 during late gestation in gilts reduces stillbirth and increases birth weight thereby improving their reproductive performance.