Coal, natural gas, and crude oil are major sources of energy. But they are nonrenewable and continuously pollute the environment. Using renewable energy resources such as biogas is one solution to address these issues. However, the hydrolysis of substrate during anaerobic digestion poses a bottleneck in biogas production. To overcome this challenge, pretreatment of lignocellulosic material before anaerobic digestion is vital. In this study pretreatment of water hyacinth via microwave assisted alkaline solution was performed to enhance its digestibility for biogas production. Water hyacinth biomass was characterize before and after pretreatment via proximate and ultimate analysis. The result of this study shows raw water hyacinth had 29.81±1.54%, 43.54±0.97%, and 16.17±2.91% of cellulose, hemicellulose, and lignin content respectively. The effects of alkali (NaOH) concentration (1, 2.5, and 4%), irradiation time (5 min, 10 min, and 15 min), and microwave power (300W, 550W, 800W) on lignin removal, and cellulose content were investigated by employing full factorial design. Results indicated that all independent variables have a significant effect (p<0.05) on the responses variable. Numerical optimization on pretreatment conditions indicates that the optimum value for alkaline concentration, microwave power, and irradiation time were 4%. 604.12watt and 13.55 minute respectively. Under this optimal condition, maximum lignin removal and cellulose content of 74.04 % and 67.73 % respectively were obtained. From physicochemical characteristics results, SEM revealed that microwave alkali pretreatment changes the compact and dense structure to a more porous and disrupted structure which is suitable for hydrolytic bacteria. Similarly, XRD analysis indicate microwave alkali treatment increase crystallinity of water hyacinth due to the removal of amorphous lignin and hemicellulose Anaerobic digestion experiments were performed on raw and optimally pretreated water hyacinth in a semibatch anaerobic digestion for 43 days. The result showed that a cumulative biogas of 5.33 ml/g VS and 7.04 ml/g VS with a methane content of 48.5% and 62% respectively were obtained from raw and pretreated water hyacinth biomass. Generally, pretreated water hyacinth gives higher biogas with better methane content (62%) in a short period of time than unpretreated water hyacinth. Therefore, microwave assisted alkaline pretreatment efficiently enhance water hyacinth digestibility for biogas production. Keywords: Anaerobic Digestion, Alkali Pretreatment, Biogas, Microwave