The objectives of this study were to determine the effects of supplementing rumen protected (RP) Lys and His individually or in combination in a diet containing hydrolyzed feather meal (HFM) on milk production and composition and energy and N partitioning in dairy cows. Multiparous Jersey cows (n = 12; 91 ± 18 d in milk) were used in a triplicated 4 × 4 Latin square with 4 periods of 28 d (24-d adaptation and 4-d collection). Throughout the experiment, all cows were fed the same TMR (17.1% crude protein, 1.64 Mcal/kg of net energy of lactation) with HFM inclusion at 5% of diet DM. Cows were grouped by dry matter intake and milk yield and cows within a group were randomly assigned to one of 4 treatments: no RP Lys or RP His; RP Lys only [70 g/d of Ajipro-L (approximately 23 g/d of digestible Lys); Ajinomoto Co., Inc., Tokyo, Japan]; RP His only [32 g/d of experimental product (approximately 8 g/d of digestible His); Balchem Corp., New Hampton, NY]; or both RP Lys and His. Data were analyzed with a model that included the fixed effect of Lys, His, and 2-way interaction and the random effect of period, square, cow within square, and error. For milk production and components, no Lys effect or interactions were observed (P > 0.14). Supplementing RP His increased (P < 0.10) milk yield (22.5 vs. 21.6 ± 2.04 kg/d) and milk protein yield (0.801 vs. 0.772 ± 0.051 kg/d). Across treatments, dry matter intake (18.5 ± 0.83 kg/d), energy supply (48.8 ± 2.21 Mcal of metabolizable energy/d) and N partitioning were not observed to differ (P > 0.10). With RP His, plasma concentration of His increased (P = 0.06; 21.8 vs. 18.7 ± 2.95 µM). Plasma Lys concentration increased when RP Lys was supplemented without RP His (77.7 vs. 66.0 ± 4.69 µM), but decreased when RP Lys was supplemented with RP His (71.4 vs. 75.0 ± 4.69 µM; interaction P = 0.04). Our results suggest that His may be a potentially limiting AA in high-HFM diets and that supplementation of RP His may increase milk and milk protein production. No response to RP Lys suggesting that Lys was not limiting.