The current study investigated the in vitro degradability, in vitro gas production, methane (CH) production, and ruminal bacterial community of kenaf plants cut at different heights (130, 160, 190, 220, and 250 cm). These samples were subjected to an in vitro batch culture system using buffalo rumen fluid to measure gas and CH production at 3, 6, 9, 12, 24, 36, 48, and 72 h of incubation. Results reveal that crude protein (CP) concentration was the highest at the 220 cm height compared with the other heights. With the increase in height, gas and CH production decreased. However, the CH production at 190 cm was higher compared with the other plant heights. Dry matter degradation was higher at 190 cm and 220 cm, while ammonia-N and microbial CP were higher at the 220 cm height compared with the other heights. However, neutral detergent fiber degradation was the highest at the 130 cm height. Total volatile fatty acids, acetic acid, acetic acid/propane ratio, and pH value did not differ among the treatments, except for propionic acid, which was higher at the 130 cm and 160 cm heights. Overall, harvesting kenaf at plant heights of up to 220 cm was better in terms of its promising nutritional quality, improved dry matter degradation, and microbial CP contents.