The effects of fungal additives, Aspergillus oryzae fermentation extract (AO) and Fomitella flaxinea culture (FF), on milk production and ruminal fermentation characteristics, pH, VFA concentration, and NH₃-N concentration, in lactating cows were compared. Nine Holstein cows in mid-lactation (140 days in lactating period) were assigned to one of three diets; control, AO and FF for 12 days for each three replication in a switchback design. Cows were housed in a stanchion barn and fed individually twice a daily for restricted feeding. Daily milk production from the cows fed AO (19.32㎏) and FF (20.89㎏) were higher than those from the cows fed control diet (17.64㎏), (P$lt;0.05). Daily 4% FCM production from the cows fed FF (20.67㎏) was higher than that from the cows fed control (17.95㎏) and AO (17.65㎏), (P$lt;0.05). Milk fat, milk protein and solid-non-fat contents of milk from the control cows (3.92%, 3.29% and 9.66%) were higher than those of milk form the cows fed AO (3.53%, 3.10% and 9.05?b) and lower than those from the cows fed FF (3.93%, 4.13% and 10.64%), (P$lt;0.05). Fat acid composition of milk fat from the cows fed fungal additives tended to be varied compared to that from the cows fed control diet. Ruminal pH from cows fed FF (6.58) was higher than those from the cows fed control diet (6.41) and AO (6.38), (P $lt; 0.05). Total VFA concentration for FF group (340.87 mM/ ℓ ) was higher than those for the control group (286.37 mM/ℓ ) and AO group (239.27 mM/ℓ ), ( P $lt; 0.05). Ruminal NH₃-N concentrations were similar between the control (15.35 ㎎/㎗) and additive groups (15.39 and 16.25 ㎎/㎗).