Abstract: Background and Objective: Mannanase is a decomposer of the compound mannan, which is produced by many microorganisms including bacteria. This enzyme can be utilized in various industrial processes, such as in the animal feed industry to increase the nutritional value of the feed. This study aims to optimize the production and function of the mannanase enzyme, which is produced by Bacillus amyloliquefaciens on a coconut waste substrate. Methodology: This study was designed in the form of laboratory experiments described herein and repeated 3 times. The substrate dose, incubation time, optimum pH and temperature of the mannanase enzyme were measured. Results: The results of this study showed that the best conditions were a substrate ratio of 80% coconut waste to 20% tofu waste, a 48 h incubation time, a pH of 6.5 and a temperature of 40°C yielding a mannanase enzymatic activity of 5.13 U mL–1. When locust bean gum was added to the substrate composed of coconut and tofu waste, the best conditions were a dose of 0.6%, a 48 h incubation time, a pH = 6.5 and a temperature of 40°C yielding a 5.92 U mL–1 mannanase enzymatic activity. Conclusion: It is concluded that the activity of the mannanase enzyme with the substrate composed of coconut and tofu waste is not much different from that with the substrate containing locust bean gum, with the difference being only 13.34%.