Cellulose-magnetite nanocomposites were fabricated via the adsorption of magnetite onto the surfaces of functionalized nanocellulose, using different organic and inorganic acids. The properties of functionalized nanocellulose derivatives and cellulose-magnetite nanocomposites were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray, Fourier transform infrared spectroscopy (FTIR), magnetic properties measurements, and thermal analysis. The catalytic activity of the functionalized nanocellulose and cellulose-magnetite nanocomposites was evaluated towards the esterification of oleic acid with methanol for the production of methyl oleate (biodiesel). The sulfonated cellulose-magnetite nanocomposite (MSNC) showed the highest catalytic activity toward the esterification reaction (96%) due to the high dispersion of the Lewis acid sites resulted from the impregnation of magnetite (0.98 wt%) in addition to the already presented Bronsted acid sites in the surface of the nanocellulose. (C) 2017 Elsevier B.V. All rights reserved.