This study focuses on the chemical and thermo-physical characterization of date palm fiber, which can be used in the reinforcement of green composites. Alkaline solutions with different concentrations of NaOH (0.5, 1, 2 and 3%) and various immersion times (0.5, 1, 2, 4, 6 and 8h) at room temperature were used to treat fibers obtained from date palm fruit branches. In total, 750 samples were tested, and the results obtained show that the chemical treatment of the fibers can lead to an increase, up to 3 times, of their mechanical properties (strength and Young’s modulus) in quasi-static tensile tests. Due to the dispersion in the experimental data, a statistical approach is required to evaluate the mechanical properties. To better understand the phenomena related to the physico-chemical properties of these fibers, several characterization techniques have been used, namely Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray diffraction. The data have been compared with results reported in the literature for other lignocellulosic fibers.