This study investigate extraction and green hydrophobic modification of cellulose from oil palm waste in aqueous medium. Cellulose is isolate from empty oil palm bunch (EOPB) and palm frond (PF), respectively, and modify in an aqueous medium using benzoyl chloride to produce cellulose benzoate esters. Characterization is performed using X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy disperse X-ray spectroscopy (EDX). The green synthesis techniques using water and sodium hydroxide as a reaction medium is fast, safe, eco-friendly, save cost, effective, and the product is pure. From XRD results, the crystallinity of cellulose isolate from EOPB and PF is 66.12% and 71.98%, while the crystallinity of hydrophobically modified cellulose is 61.38% and 61.6%, respectively. EDX results show that isolated cellulose is very pure (> 98% pure) and have carbon and oxygen as major elemental composition. TGA, EDX, SEM and FTIR show that the integrity of the cellulose structure is well-preserved after modification in the aqueous medium. Hence, cellulose isolated from oil palm waste and modified via green synthesis techniques can be used as commercial cellulose. Also, the green synthesis technique gives very pure modified cellulose products and solves problems of environmental challenges often associated with other methods of chemical modification of cellulose.