Producers utilize foliar fungicide on whole-plant corn silage (WPCS) to minimize disease prevalence and improve forage quality. However, limited research is available on the performance effects in dairy cattle fed fungicide-treated WPCS. Therefore, the objective of this study was to determine the effects of foliar fungicide applied at vegetative tassel stage on 2 corn varieties (floury, FLY; brown midrib, BMR) on performance in primiparous and multiparous Holstein cows. Thirty-two lactating Holstein cows [BW = 649 ± 74 kg; DIM = 189 ± 49 d] were assigned to 1 of 4 treatments in a 4 × 4 Latin square design: FLY and fungicide (FF), FLY and no fungicide (control; FC), BMR and fungicide (BF), and BMR and no fungicide (BC). Silage was inoculated (Silo-King; Agri-King, Fulton, IL) and ensiled for 295 d in an Ag-Bag (Ag-Bag; St. Nazianz, WI). Statistical analysis was performed using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC). There were no differences in dry matter intake between the 4 treatments (P > 0.10). Milk yield was greater for cows in non-fungicide treatments (33.61 ± 0.63 kg/d) compared with cows in fungicide treatments (31.46 ± 0.63 kg/d; P = 0.01). Milk fat percentage was greater for cows in BF (3.85 ± 0.11%) compared with cows in BC (3.70 ± 0.11%; P = 0.009). Protein yield was greater for cows in FC (0.98 ± 0.02 kg/d) compared with cows in FF (0.92 ± 0.02 kg/d, P = 0.001). Protein percentage was greater for cows in non-fungicide treatments (2.97 ± 0.05%) compared with cows in fungicide treatments (2.92 ± 0.05%; P < 0.001). Milk urea nitrogen was greater for cows in non-fungicide treatments (14.45 ± 0.23 mg/dL) compared with cows in fungicide treatments (14.03 ± 0.23 mg/dL; P < 0.001). In conclusion, foliar fungicide application neither hindered nor improved DMI. However, fungicide application may lead to a decreased milk yield and milk components, as well as an alteration in nitrogen utilization.