The extraction of nanocellulose from agro-waste have received wide attention in nanocomposite technologies. This research unravels physico-chemical characteristics of cellulose from Malaysia Indica rice straw, and the derived cellulose nanocrystal (CNC) by hydrochloric acid (HCl) hydrolysis. The CNC was subjected to field emission scanning electron microscopy (FESEM) and/or transmission electron microscopy (TEM) and Fourier transformed infrared (FTIR) studies. Furthermore, X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS) were compared with TEM for the CNC lateral crystal size. Subsequently, CNC reinforced epoxy laminates for Kevlar were prepared and tested for their tensile properties. While FTIR analysis confirmed the monoclinic cellulose structure of the isolated CNC, XRD, and SAXS were compared with TEM for the CNC lateral crystal size. Hydrolysis of the cellulose sample yielded 40.87% of CNC with 4.8 nm in width and a needle-shaped nature. The extracted CNC has relatively low crystallinity (56.12%) but interestingly low crystallite size with an average crystallite size of 1.69 nm (XRD) and 4.18 nm (SAXS). Furthermore, an addition of just 1 wt% of CNC to epoxy composite increased the strength of Kevlar by over 300% and the elastic modulus by nearly three-fold. Nanocellulose obtained from rice straw have great potential as reinforcing agents for the manufacture of nanocomposites.