The experiment aimed to evaluate the effect of replacing elephant grass (EG) silage with jackfruit leaves (JL) silage in the diet on in vitro nutrient digestibility, ruminal fermentation, and methane production using ruminal fluid from crossbred Saanen goats. The study was conducted using a completely randomized design, and treatments were developed by replacing EG silage with JL silage on a DM basis) at rates of 0, 25, 50, 75 and 100%, corresponding to JL0, JL25, JL50, JL75 and JL100. All diets were formulated to maintain a roughage-to-concentrate ratio of 60:40. The in vitro digestibility of DM, organic matter (OM), and crude protein (CP), as well as the concentration of NH3-N, were not influenced (P>0.05) by the inclusion of JL silage in the diet. However, the digestibility of neutral detergent fiber (NDF) tended to increase (P=0.083; quadratic effect) in JL25 but gradually decreased as the replacement level increased to 100%. The total concentrations of volatile fatty acid (VFA) did not differ (P>0.05) among the treatments, although individual VFA concentrations altered (P4 and CO2 volumes were not changed (P>0.05) by increasing the proportion of JL silage in the diet. The results of this experiment suggest that JL silage can completely replace for EG silage in goat diet containing 40% concentrate without negative impact on in vitro nutrient digestibility and ruminal fermentation.