Bacterial nanocellulose (BNC) is an emerging nanomaterial that has drawn immense attention due to its unique physical and chemical properties. This chapter mainly focuses on the recent developments in the design, synthesis, and application of novel BNC-based multifunctional nanocomposites. The robust bio-mediated synthesis of nanocellulose network when combined with versatile in situ and post-modification strategies enables the incorporation of various functional nanomaterials into the nanocellulose network. These BNC-based multifunctional nanocomposites are highly promising for water treatment, energy harvesting, chemical sensing, catalysis, and life sciences. However, there are several outstanding challenges associated with BNC such as high production cost and durability that need to be addressed before these composites can be widely deployed in the real world. Despite the challenges, owing to their unique structure and properties, BNC-based nanocomposites will attract increased for various applications.