This study aimed to evaluate the effect of replacing jackfruit leaves (JF) for Para grass (PG) on intake, digestibility, nitrogen balance, ruminal fermentation, milk yield and composition in lactating goats. Four crossbred Saanen lactating goats in mid-lactation and milking 1676 ± 112 g/day were used in a 4 × 4 Latin square design. A basal diet consisted of concentrate and PG (C:F 40:60). Treatments were dietary replacement of JL for PG at ratios of 0, 50, 75 and 100% corresponding to JL0, JL50, JL75 and JL100 diets, respectively. Feeding JL increased linearly (P < 0.01) DM intake, but decreased linearly (P < 0.05) nutrient digestibility. A linear increase in fecal N (P < 0.01) and N retention (P = 0.04), but a linear decrease in urinary N (P = 0.03) was detected when increased the JL in the diets. Total VFA concentration increased quadratically (P = 0.04), and the highest value was observed in JL75 compared with JL0 (85.9 vs. 72.8 mM). Milk production increased linearly (P = 0.03), but no change was observed in milk composition and blood urea nitrogen (BUN). Overall, combined data suggest that the substitution of JL for PG in lactating goat diets is effective in the improvement of nutrient intake, N retention, ruminal VFA concentration and milk yield without affecting milk composition and BUN.