Abstract: Background and Objective: The utilization of oil palm fronds (OPFs) as feed is limited due to their high lignin content. The biodelignification of OPFs with Phanerochaete chrysosporium plus the elements Ca and Mn can break down lignocellulose and lignin hemicellulose bonds. Supplementation of fermented oil palm fronds (FOPFs) with P, S and Mg results in the highest microbial protein synthesis and VFA concentration. The objective of this study was to evaluate the effect of supplementation with phosphorus, sulfur and magnesium in goat rations containing fermented oil palm fronds (FOPFs; fermented by Phanerochaete chrysosporium) on nutrient digestibility. Materials and Methods: This research was carried out using a randomized block design with 5 treatments and 3 replications. The following treatments were performed: A = 40% Napier grass (NG)+0% FOPFs+60% concentrate; B = 20% NG+20% FOPFs+60% concentrate; C = 0% NG+40% FOPFs+60% concentrate; D = 20% NG+20% FOPFs +60% concentrate plus P, S and Mg and E = 0% NG+40% FOPFs+60% concentrate plus P, S and Mg. The data were analyzed using a one-way analysis of variance (ANOVA) and differences between treatments were tested using Duncan's multiple range test (DMRT).The observed parameters were digestibility of the nutrients. Results: Supplementation with phosphorus, sulfur and magnesium in goat rations that contained fermented oil palm fronds by Phanerochaete chrysosporium at concentrations of 40 and 60% resulted in the highest digestibility of the nutrients. Conclusion: Supplementation with P, S and Mg in goat rations containing FOPFs is indispensable for the growth and activity of rumen microbes.