Monensin and essential oils can manipulate ruminal fermentation profile. We evaluated the effect of a microencapsulated blend of capsaicin, carvacrol, cinnamaldehyde, and eugenol (CEO. 200 mg/kg of TMR DM) relative to monensin (MON. Fifteen mg/kg of TMR DM) or control (CTL) on lactation performance, intake pattern, rumen fermentation profile, and diet digestibility of dairy cows. Thirty individually fed Holsteins (189 ± 83 DIM) received a standard diet for 14 d and a treatment for 56 d, in a covariate adjusted randomized block design with repeated measures over time. Pre-planned contrasts were C1) CTL vs. CEO and C2) CEO vs. MON. The CEO increased milk protein secretion compared with MON (+ 51 g/d, P = 0.04) and tended to increased relative to CTL (+ 38 g/d, P = 0.12). The CEO also tended to increase milk yield relative to CTL (33.0 vs. 34.4 kg/d, P = 0.11) and ECM (+ 1.3 kg/d, P = 0.15) and fat yield (+ 60 g/d, P = 0.13) relative to MON. Cows on CEO had greater covariate adjusted BW and daily gain (P < 0.01) and tended to have higher BCS (P = 0.13) than CTL. The DMI (21.0 kg/d), milk/DMI (1.59), ECM/DMI (1.51), the total-tract apparent digestibility of OM and NDF, and the digestible OM intake (DOMI) were similar among treatments (P ≥ 0.25). Urinary allantoin excretion was reduced by MON (P ≤ 0.05 for C2). The CEO increased the proportion of acetate in ruminal VFA (P = 0.04 for C1 and P = 0.02 for C2) and reduced butyrate (P = 0.05 for C1 and P = 0.03 for C2) and methyl-butyrate (P = 0.13 for C1 and P = 0.01 for C2), and MON tended to increase propionate (P = 0.12 for C2). The A/P ratio tended to be increased by CEO (P = 0.12 for C1 and P = 0.07 for C2). Cows on MON had lower proportion of the daily intake at night and selected in favor of small feed particles in the afternoon (P ≤ 0.01 for C2) and CEO induced more refusal of long feed particles in the morning (P = 0.02 for C1). Rumination/DMI tended to be reduced by CEO (P = 0.06 for C1 and C2) and total chewing/DMI was reduced compared with MON (P = 0.05 for C2). The CEO had no effect on diet digestibility and feed efficiency, but increased acetate in rumen fluid, weight gain, and lactation performance.