Feeding direct-fed microbials (DFM) to lactating dairy cattle has been demonstrated to improve milk production efficiency and alter milk composition. The objectives of this experiment were to evaluate the effects of feeding a DFM on milk production, feed intake, and milk composition of midlactation dairy cows. Forty-eight multiparous Holstein cows were assigned randomly to one of 2 treatment: 1) a basal control diet (CON) top-dressed with 100 g of ground corn or 2) a basal control diet top-dressed with 96 g of ground corn and 4 g of a lactate-producing direct-fed microbial (DFM; 10-G; Life Products, Inc., Norfolk, NE). All cows had ad libitum access to feed (offered at 0800 and 1600 h) via individual feeding gates and were milked 3 times daily (0800, 1400, and 2000 h). Milk production and feed intake were recorded daily whereas BW, BCS, and milk components were determined weekly over the experimental period (14 weeks). Data were analyzed by using repeated measures in the MIXED procedure of SAS. Cows supplemented with DFM had similar milk yield compared with CON cows (40.8 and 41.5 ± 1.80 kg/d, respectively P = 0.76). Likewise, DMI was similar for both treatments and averaged 26.2 ± 0.58 kg/d (P = 0.77). Milk urea nitrogen tended to decrease in DFM cows compared with CON cows (12.84 vs 13.44 ± 0.28 mg/dL, respectively; P = 0.13). The trend for lower MUN was accompanied by a concomitant numerical increase in milk protein percentage in DFM cows compared with CON cows (3.24 vs 3.18 ± 0.05%, respectively; P = 0.37) with no differences in milk fat concentration (average 3.82 ± 0.12% for both treatments; P = 0.88), thus resulting in similar yield of energy corrected milk (43.73 ± 1.84 kg/d; P = 0.88). Interestingly, SCC was reduced (P = 0.03) from 278,800 to 103,900 ± 53,700 cells/mL when cows were supplemented with DFM. Similarly, log₁₀-transformed SCC from cows consuming DFM tended to decrease compared with CON cows (P = 0.11). Supplementing DFM to lactating Holstein cows appears to improve milk nitrogen use efficiency and decrease SCC while maintaining DMI and milk production.