Multiparous Holstein cows (n = 122) were used in a randomized block design to determine the effect of Scutellaria baicalensis extract (SBE) on 305-d milk yield and milk markers of inflammation and metabolic function. Treatments were 1) control, 2) 5-d administration of SBE (SBE5), and 3) 60-d administration of SBE (SBE60). Treatments were included in a treatment pellet that was identical to the control pellet except for the extract, both provided via an automated milking system beginning on d 1 of lactation. Milk samples were collected on d 1, 3, and once during d 5–12 of lactation, followed by weekly sampling until 120 d in milk. Milk samples collected in the first 2 wk were used for biomarker analysis (haptoglobin, β-hydroxybutryate [BHB], and glucose-6-phosphate [G6P]) and all samples were used for component analysis. Milk production, programmed pellet allocation, and actual provision of both pelleted feeds were recorded daily. Treatment effects were evaluated by contrasts between control and SBE5 and control and SBE60 for both the treatment (TP; wk 1–9) and carryover periods (CP; wk 10–37). Total pellet allocated was greater for SBE60 in both the TP (P < 0.01) and CP (P = 0.02), but was not different for SBE5 during either period (both P > 0.12). No treatment effects were observed for milk haptoglobin, BHB, or G6P (all P > 0.88). SBE5 did not alter milk yield (P = 0.60) or milk components (P > 0.10). SBE60 increased whole-lactation milk yield (P = 0.03). SBE60 increased milk lactose and fat yields (P < 0.05) and tended to increase milk protein yield (P = 0.09) during TP, and each increased during CP (P < 0.05). Somatic cell count decreased in SBE60 during TP (P = 0.02) but not CP (P = 0.13). Mastitis incidence tended to differ by treatment (P = 0.06), being lesser for SBE5 (P = 0.04) and SBE60 (P = 0.05) vs. control. SBE60 tended to decrease the hazard of leaving the herd compared with control and SBE5 (P = 0.07). In conclusion, supplementation of postpartum dairy cows with SBE for 60 d was effective at increasing whole lactation milk yield.