In this study, we propose for the first time the use of Cr(NO3)3 hydrolysis system as an efficient and sustainable technique for producing nanocellulose. Many papers have reported the combination of metal salts and mineral salt or mechanical process for hydrolyzing the cellulosic feedstock into hydrocellulose or nanocellulose, but there is limited research on the involvement of metal ion catalyst alone to produce cellulose nanocrystals (CNC) without the addition of any mineral acid or assistance of mechanical treatment. The main objectives of this study include the following: (i) exploiting the feasibility and practicability of Cr(NO3)3 as a high potential catalyst for converting cellulose into its nanostructured morphology; (ii) optimizing the reaction conditions of Cr(NO3)3 hydrolysis system in order to produce a high performance nanocellulose; and (iii) evaluating the physicochemical changes in terms of functional groups (Fourier transform infrared; FTIR), crystalline structure (X-ray diffraction; XRD), morphological properties (Field emission scanning electron microscopy; FESEM and transmission electron microscopy; TEM) and thermal stability (Thermogravimetric analysis; TGA) during the production of nanocellulose from macro-sized native cellulose. We also attempted to produce CNC from the same starting material by concentrated H2SO4 hydrolysis, in order to perform a comprehensive comparison and assessment between resulting nanocellulose (CNCCr(NO3)3 and CNCH2SO4) using a similar analytic instrument systematically. We used microcrystalline cellulose (MCC) as a starting material instead of extracted cellulosic pulp from lignocellulosic biomass to better understand the role of Cr(NO3)3 hydrolysis system in the conversion of cellulose, avoiding impure bulk materials that might cause irreproducible results.