The utilization of cellulosic fibers is becoming increasingly widespread worldwide as promising raw material in polymer composite reinforcement. However, and despite the multiple advantages of cellulosic fibers like the lower density, cheap cost and biodegradability, their use is limited due to hydrophilic character which reduces their affinity with hydrophobic matrices. A natural fiber treatment, whether chemical or physical, is advised to address this issue. The purpose of this study is to characterize the Ampelodesmos mauritanicus plant (AM) fibers extracted by the chemical method (2% NaOH for 48 h) and treated (chemically and physically). We carried out acetylation, mercerization and microwaves modification of the AM plant fibers to reduce their hydrophilic character. The influence of chemical and physical treatments on the structure and morphology of AM plant fibers was characterized by analytical techniques as per International Standard. X-ray diffraction confirmed that the AM fibers have a good crystallinity index (52.4%). Microwave physical treatment at 550 W increased their density from 1.00 to 1.55 g/cm3, their Young’s modulus and tensile strength from 11.0 to 18.6 GPa and from 155 to 290 MPa, respectively, giving the highest values. It is followed by chemical treatments: first with acetic anhydride (C4H6O3) for 4 h and then with 3% NaOH also for 4 h. It should be observed that the data have a very considerable dispersion that calls for statistical analysis (method of Weibull with two and three parameters was utilized).