Particles of filler materials are often added to polymers to alter their characteristics, modify their processing, and increase the composite material’s cost-effectiveness. CaCO3, TiO2, Al2O3, CNT, and SiC are just a few of the synthetic fillers that have received a lot of study during the past half-century. Nonetheless, researchers began thinking about alternatives to polymeric materials as fillers due to environmental and dwindling natural resource issues. Much progress has been made in the previous two decades, and the industry is shifting toward green fillers. Polymer composites’ low-cost, high specific strength, and low weight make them a popular material choice for a wide range of commercial, residential, and transportation uses. Finding the right nanofiller to utilize in polymer composites can improve their functionality in several ways. Incorporating natural fibers and nanofillers into polymer composites creates a material that is both versatile and friendly to the environment (aerospace, automobile industries, electronics, biomedical, etc.). Renewable and biodegradable materials have increased as people have become more aware of the harm petroleum-based fibers pose to the environment. As the market for sustainable materials continues to increase, producers of automobiles and scientists developing new materials are being forced to evaluate the environmental impact of their products at every stage of production, from raw material extraction through final disposal. Due to their many advantageous properties, including renewability, environmental environmentally friendly, recyclable, biodegradable, lightweight, stronger in particular strength, resistant to impact and corrosion, cheap to produce, simple to work with, and abundantly available natural fiber-reinforced composites (NFRC) have been widely adopted in the automotive industry over the past decade. The transportation industry has pushed for the widespread adoption of NFRC as a lightweight and cost-effective alternative to composites made of petroleum and synthetic fibers like aramid as well as kevlar, along with carbon, and glass are used for a broad range of automotive components, including door panels, instrument panels, bumpers, spoilers, seat coverings, and mirror frames. Incorporating organic or inorganic nanofillers into plant fiber-reinforced composites can enhance their mechanical, tribological, and thermal characteristics. The integrated structure of polymeric nanocomposites (PNCs) demonstrates capabilities that none of its component materials separately possesses, making it a top pick for use in a myriad of contexts. Stimulus-responsive PNCs are characterized by at least one chemical or physical property that responds to an external stimulus or is controlled by external stimulus nanocomposites. The three major types of green nanofillers are derived from plants, animals, or the earth itself. New developments in environmentally friendly nanofillers were also covered. This chapter provides an overview of the nanofiller-based polymer composite and the difficulties encountered during processing. Nanofillers are increasingly being used to improve the mechanical characteristics (tensile, flexural, impact, and tribological) and, most crucially, the self-healing capability of polymer composites, leading to an explosion in their utilization. Natural fiber-reinforced composites are discussed in this chapter, along with a summary of the impacts of various chemical reagents, production procedures, and industrial use.