The usage of direct-fed microbials (DFM) has become common in the dairy industry, but questions regarding their value and mode of action on dairy cows performance remain prevalent. The objective of this study was to evaluate the effects of DFM (Bacillus pumilus 8G-134) on pre- and postpartum performance. Forty-three multiparous Holstein cows were fed a total mixed ration (TMR) according to NRC (2001) recommendations and assigned to 2 treatments in a randomized completely block design. Cows in the direct-fed microbial treatment (DFMt, n = 21) received 5.0 × 10⁹ cfu of B. pumilus 8G-134 direct-fed microbial in 28g of maltodextrin carrier, whereas cows in the control treatment (CON, n = 22) received 28g of maltodextrin carrier alone. Treatments were top-dressed on the TMR daily. Treatments were applied from 21 d before expected calving date to 154 d after calving. Intake from each cow was measured and dry matter intake was recorded daily. Milk weights were recorded daily, and milk samples were obtained weekly. Composite milk samples were analyzed for fat, protein, lactose, urea N (MUN), total solid and somatic cell count (SCC). Statistical analysis was performed using the MIXED procedures of SAS. Cows on DFMt had higher milk yield (41.2 ± 1.34 vs. 37.8 ± 1.33 kg; P = 0.02), fat corrected milk (48.5 ± 1.48 vs. 42.0 ± 1.49 kg; P = 0.01), energy-corrected milk (46.6 ± 1.40 vs. 40.9 ± 1.38 kg; P = 0.01), fat production (1.85 ± 0.06 vs. 1.57 ± 0.06 kg; P = 0.03), and protein production (1.27 ± 0.04 vs. 1.18 ± 0.04 kg; P = 0.02) on the second week of lactation than CON. There were no differences (P > 0.27) between treatments for milk yield, fat, protein, lactose, total solids, MUN or SCC overall. Dry matter intake, BW, body condition score (BCS) were not affected (P > 0.35) by DFMt supplementation. Cows on DFMt tended (P = 0.06) to have higher feed conversion (ECM/DMI; 2.02 ± 0.04) than cows fed CON (1.92 ± 0.04). In conclusion, cows fed DFMt tended to have higher feed conversion than CON with no detrimental consequences (i.e., BCS).