Background and Objective: Palm fronds and rice straw are agricultural wastes that have the potential to be utilized as feed for ruminants but have low quality. The high fraction of crude fibre of palm fronds and rice straw, namely, cellulose, hemicellulose and lignin, causes their use as feed to be limited. Therefore, it is necessary to improve the quality through fermentation that involves such microorganisms as the bacteria found in probiotics. Probiotics containing cellulolytic, mannanolytic and lactic acid bacteria represent a notable opportunity to improve the quality of feed ingredients. This study aimed to determine the nutritional contents of palm fronds and rice straw fermented with probiotics containing cellulolytic, mannanolytic and lactic acid bacteria. Materials and Methods: This study employed a completely randomized design with a 3×3 factorial pattern and with 4 replicates. Factor A is the percentage of probiotics, namely, A1 = 0%, A2 = 2% and A3 = 4% and factor B is the waste used, namely, B1 = palm frond B2 = rice straw and B3 = 50% palm frond + 50% rice straw. Results: The results showed that there was an interaction between the provision of probiotics and agricultural waste (palm fronds and rice straw). The interaction between the provision of 4% probiotics with the combination of palm fronds and rice straw (A3B3) showed that the contents of crude protein, crude fat, phosphorus and NDF were better than for the other combinations. As much as 4% of probiotics in rice straw showed the best contents of calcium, crude fibre, ADF and cellulose. The interaction between 2% probiotics and rice straw (A2B2) exhibited the best lignin content. The fermentation treatment using probiotics produced a positive response in reducing the fibre fraction. Conclusion: The provision of 4% probiotics in the combination of palm fronds and rice straw demonstrated an increase in quality values.