In the babassu oil extraction industry, several types of by-products are generated, and one of them is the mesocarp, which when dried and ground, is transformed into a flour that is called “Babassu Mesocarp Flour” (BMF). Thus, the use of the BMF as a bio-reinforcement for Poly(Lactic Acid) (PLA) aiming at the production of composite films applied in food packaging is a promising alternative, which leads to the development of new products with added value. Therefore, in this work, before any attempt to produce films, the industrially extracted BMF was characterized for a better understanding of its chemical composition and inherent characteristics. The elemental analysis showed that this raw material is predominantly an organic material, however, it also presented contents of inorganic chemical elements according to the X-ray fluorescence analysis. Its particles exhibited an average diameter of 38.82 µm and a specific surface area of 3.02 m2/g. Through microscopic techniques, mainly by scanning electron microscopy, starch granules in different shapes and sizes were observed, since starch is the main component of the composition of this raw material. The results of X-ray diffraction and infrared spectroscopy showed a structure and functional groups, respectively, typical of starchy materials, evidencing the sustainable and biodegradable character of the BMF. The reported characteristics of the BMF are of great value in PLA-based film formulations, as this combination would reduce impacts on the environment, as both are ecologically correct.