This study investigated the effects of condensed tannin (Quebracho Colorado) supplementation on milk yield and composition, intake, blood and rumen parameters, and digestibility in early–lactating dairy cows. Twenty–four cows were assigned to three groups: control (CON, n = 8), T1 (60 g of tannin, n = 8) and T2 (120 g of tannin, n = 8). Milk yield was recorded twice daily (at 08:00 and 16:00). Blood and rumen fluid samples were collected on days 0, 15 and 30 for the analysis of ammonia, pH, volatile fatty acids and blood metabolic profile. Over the last 5 days, faecal samples were collected to determine digestibility and conduct wet sieving particle size evaluation. The results showed no significant differences between the T1 and T2 groups in terms of milk yield, but both groups had higher milk yield than the CON group (P < 0.05). The energy–corrected milk yield (ECMY) and ECMY to dry matter intake (DMI) ratio (ECMY/DMI) were the highest in the supplemented groups. Blood analysis revealed higher blood Ca levels in CON than T1, and lower Mg levels in CON compared to T2. Protein digestibility was the highest in the T2 group. Rumen ammonia levels were the highest in the CON group and the lowest in the T2 group (P < 0.05). Acetic, propionic and butyric acid levels increased in the T1 and T2 groups. Faecal sample from the T2 group had lower particle retention on the second (middle) sieve (P < 0.05). So, the addition of 60 and 120 g of tannin exerted a positive effect on milk yield, feed utilisation, ruminal ammonia, volatile fatty acids, milk parameters, and protein digestibility. Therefore, quebracho tannin can be considered as a potential means to mitigate the effects of negative energy balance in dairy cows.