Efficient use of the entire lignocellulosic biomass is important for biorefinery sustainability, especially considering the extraction of high value-added products, such as nanocellulosic materials. This work investigates the feasibility of using sugarcane straw as a feedstock to obtain lignocellulose nanocrystals (LCNCs). Together with bagasse, the straw is a residue from the processing of sugarcane in the ethanol/sugar mills, but its effective use remains to be further studied. An organosolv pretreatment process was first applied to the straw for partial removal of the lignin and hemicellulose contents (reductions of 72.2 and 62.1 %, respectively) and to increase the surface area (observed by scanning electron microscopy and atomic force microscopy). Acid hydrolysis carried out for different reaction times, with or without mechanical treatment, resulted in high yields of sugarcane straw LCNCs (40–64 % of the total mass). X-ray diffraction analyses showed that the crystallinity of the LCNCs increased from 65 to 80 %, with an estimated average elementary crystallite size of 3.3 nm. The aspect ratios of the LCNCs were determined by AFM and ranged from 18.0–30.1. The onset of thermal degradation of the LCNCs occurred between 145 and 191 °C. The findings demonstrated the effective extraction of cellulose nanocrystals with residual lignin from sugarcane straw, opening the possibility of obtaining high value-added nanomaterials and contributing to the sustainability of future lignocellulosic biomass biorefineries.