This study focuses on developing a nano zinc oxide (ZnO) catalyst with fly ash (FA) as a support material for converting kapok seed oil (KSO) into biodiesel. This research aims to study the preparation of nano ZnO/FA solid catalysts and the catalyst's reactivity towards kapok seed oil biodiesel (KSOB) products. The catalysts were synthesized using a modification of the Stober process, which is the co-precipitation, impregnation, and precipitation step co-occurred. The catalyst is prepared on base condition using sodium hydroxide with a solvent of methanol and zinc chloride as a raw material. FA waste was effectively modified with zinc oxide particles to create a high-performance ZnO/FA composite catalyst. Under optimal stoichiometric NaOH and 60% ZnO, the resulting material achieved a remarkable specific surface area of 14.8 m²/gram, indicating its potential for enhanced catalytic activity. The prepared catalyst of nano ZnO/FA achieved successful methanolysis of KSO, with a maximum FAME yield of 61.09% attained at 65°C after 5 hours of reaction time, using a 3% catalyst dose and a KSO: methanol molar ratio of 1:15. The initial success of nano ZnO/FA with kapok seed oil paves the way for further development towards robust catalysts specifically tailored for low-grade oil conversion.