In this dissertation, various noncrosslinked and crosslinked biobased and biodegradable polymer nanocomposites were fabricated and characterized. The properties of these polymer nanocomposites, and their relating mechanisms and corresponding applications were studied and discussed in depth. Chapter 1 introduces the research background and objectives of the current research. Chapter 2 presents the development of a novel low cost carbon source for bacterial cellulose (BC) production and fabrication and characterization of biobased polymer nanocomposites using produced BC and soy protein based resins. The carbon source, soy flour extract (SFE), was obtained from defatted soy flour (SF) and BC yield achieved using SFE medium was high. The results of this study showed that SFE consists of five sugars and Acetobacter xylinum metabolized sugars in a specific order. Chapter 3 discusses the fabrication and characterization of biodegradable polymer nanocomposites using BC and polyvinyl alcohol (PVA). These polymer nanocomposites had excellent tensile and thermal properties. Crosslinking of PVA using glutaraldehyde (GA) not only increased the mechanical and thermal properties but the water-resistance. Chapter 4 describes the development and characterization of microfibrillated cellulose (MFC) based biodegradable polymer nanocomposites by blending MFC suspension with PVA. Chemical crosslinking of the polymer nanocomposites was carried out using glyoxal to increase the mechanical and thermal properties as well as to make the PVA partially water-insoluble. Chapter 5 reports the development and characterization of halloysite nanotube (HNT) reinforced biodegradable polymer nanocomposites utilizing HNT dispersion and PVA. Several separation techniques were used to obtain individualized HNT dispersion. The results indicated uniform dispersion of HNTs in both PVA and malonic acid (MA) crosslinked PVA resulted in excellent mechanical and thermal properties of the materials, especially for the crosslinked PVA. Chapter 6 presents the biodegradation of PVA based resins and nancomposites in a composting medium. The results suggest that biodegradation of PVA based materials is mainly by enzymes secreted by fungi. The three factors, namely, crystallinity, additives and crosslinking, may be utilized effectively to enhance the life of these materials in real life applications. Chapter 7 presents broad conclusions of the the entire study and possible suggestions for future research.