Innovations in food packaging materials are driven by the demand for improved sustainability, functionality, and longer shelf life. Petroleum-based packaging, while very versatile, has its limitations regarding sustainability as it cannot be easily recycled and is non-biodegradable. Fillers and additives are added to composite packaging materials to overcome the limitations of plastic-based materials. These additives can enhance the functionality of packaging materials as they improve barrier and mechanical properties, and sustainability is considered. On the other hand, additives such as plasticizers, stabilizers, antioxidants, and antibacterial agents improve the flexibility, durability, and food preservation properties of polymer composites. Gas and moisture permeability, structural integrity, and biodegradability are improved by fillers such as starch-based materials, graphene oxide, nanoclay, and nanocellulose. To enable the widespread adoption of composite packaging materials, limitations such as cost, dispersion efficiency, recyclability, and industrial scalability must be overcome. The role and types of additives and fillers used in packaging composites are discussed in this chapter. The impact on barrier and mechanical properties, environmental considerations, emerging research, and a detailed review of future developments for sustainable food packaging are also included in this chapter.