Display omitted •Cellulose nanocrystals (CNC) were successfully extracted from Diss stems.•Chemical and enzymatic pretreated celluloses from Diss were acid hydrolyzed.•CNC from enzymatic treated fibres (E-CNC) exhibited enhanced thermal stability.•CNC from chemically treated fibres (C-CNC) have reduced size compared to E-CNC. The aim of this research activity was based on the revalorization of Amplodesmos mauritanicus (Diss), an African grass largely presented in the Algerian territory. Diss stems were selected as native botanic material for the extraction of cellulose nanocrystals (CNC). Two different pretreatment steps were carried out to extract CNC from Amplodesmos mauritanicus stems and the following acidic hydrolysis procedure allowed to extract/obtain cellulose nanocrystals in aqueous suspension. The effect of the two different pretreatments, based essentially on chemical or enzymatic treatments, were deeply investigated and the properties compared. Field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) were considered for the characterization of raw material, chemical or enzymatic treated Diss stems and CNC extracted from both chemical and enzymatic pretreated cellulose.