The increasing global demand for petroleum oils has led to a significant increase in their cost and has led to the search for renewable alternative waste resources for biodiesel synthesis and production using novel environmentally sound and acceptable methods. In the current study, Kocuria flava lipase was immobilized on Fe₃O₄/cellulose nanocomposite; and used as a biocatalyst for the conversion of cooking oil wastes into biodiesel through the transesterification/esterification process. The characterization of Fe₃O₄/cellulose nanocomposite revealed several functional groups including carboxyl (C=O) and epoxy (C-O-C) groups that act as multipoint covalent binding sites between the lipase and the Fe₃O₄/cellulose nanocomposite and consequently increasing lipase immobility and stability. The immobilized lipase showed a high thermo-stability as it retained about 70% of its activity at 80 °C after 30 min. The kinetics of immobilized lipase revealed that the K_m and V_max values were 0.02 mM and 32.47 U/mg protein, respectively. Moreover, the immobilized lipase showed high stability and reusability for transesterification/esterification reactions for up to four cycles with a slight decline in the enzyme activity. Furthermore, the produced biodiesel characteristics were compatible with the standards, indicating that the biodiesel obtained is doable and may be utilized in our daily life as a diesel fuel.