Short fiber-reinforced polypropylene is largely used in the automotive industry. Fatigue failure is one of the most failure modes observed in this class of materials. In order to better understand the damage mechanisms and plasticity evolution, this article provides an overall experimental investigation of the mechanical properties of a PPGF40 composite (polypropylene matrix reinforced by a 40% weight content of short glass fibers) including monotonic and cyclic loading. The effect of various parameters such as the loading direction, the strain rate, the temperature, and the fatigue are analyzed. The evolutions of the loss of stiffness and plastic strain during monotonic and fatigue tests are analyzed. Self-heating during cyclic loading is also studied. Moreover, the coupling effect of damage and plasticity is analyzed by plotting the evolution of the relative loss of stiffness vs the plastic strain increment for monotonic and cyclic loadings. For quasi-static loading, the results emphasize an intrinsic curve independent of the loading direction. Moreover, a sharp increase in the damage and plasticity levels due to the local effect occurring during cyclic loading is observed and correlated to SEM fracture surface analysis.