Chemical and mechanical degradation of cellulose pulp with minimal impact on cellulose fibers results in an interesting material known as nanofibrillated cellulose (NFC). As a glucose polymer with a linear structure, NFC can be easily modified by chemical means, which leads to the possibility of modifying its compatibility with a variety of polymeric matrices. Then, due to its remarkable mechanical properties, it has great potential a mechanical reinforcer for multiple materials. In UDT (Technology Development Unit, Universidad de Concepción), we have extensively studied different strategies to obtain, modify, and use NFC as mechanical reinforcer of thermoplastic and thermosetting polymers. Thu, in the following chapter, we explore and discuss our study of the potential of NFC as reinforcing additive for important products in the Chilean industry.