The main purpose of this paper is to investigate the effect of alkaline treatment on the physical, thermal, mechanical and chemical properties of pristine lemba leaves fibres (LeLeFs). LeLeFs were treated with 6, 8, and 10 wt% sodium hydroxide (NaOH) solution at room temperature for 24 h. In order to determine the functional group presence after the alkaline treatment, LeLeFs were analyzed using Fourier Transform Infrared (FTIR) Spectroscopy. The density of LeLeFs treated with 10 wt% NaOH solution recorded the highest density with 1.168 g/cm³. Morphology study showed that the diameter of fibre reduced with the increment of NaOH concentration. The removal of lignin and hemicellulose could be observed in the thermogravimetric analysis (TGA). Alkaline treatment enhanced the tensile properties of fibre and 10 wt% alkaline treated fibre resulted in the highest tensile strength, modulus and elongation of the fibre at 511.10 MPa, 11.76 GPa and 3.69% respectively. Chemical resistance analysis found that the treated fibre had better chemical resistance compared to untreated fibre. Therefore, it is substantiated that alkaline treatment affects the properties of LeLeF.