Sustainable materials sourced from renewable resources and developed using eco-friendly technologies possess the ability to impact the environmentally harmful generation and utilization patterns established during the industrial age. This literature investigates novel hybrid composite panels composed of wood, fungal mycelium, and cellulose nanofibrils. Conventional wood composites, which rely heavily on synthetic adhesives for mechanical strength, are reimagined here through the use of mycelium to enhance their properties. Additionally, the integration of experimental methods with machine learning is explored to optimize mechanical performance. This study focuses on the creation and analysis of fully bio-based hybrid composites composed of wood, fungal mycelium, and cellulose nanofibrils. These materials aim to merge the sustainability and biodegradability of mycelium with the high physical properties of cellulose nanofibrils. The hybrid composites are assessed for their physical, mechanical, and thermal characteristics, highlighting their potential use in environmentally conscious material applications. Nanocellulose improves the structural strength of biocomposite films, while mycelium lessens the usual water interaction with cellulose, leading to faster-drying fibrous slurries and films with superior water resistance compared to nanocellulose alone. These mycelium-nanocellulose biocomposites have a range of applications, such as purification, packing, and health products, and they are compatible with conventional papermaking techniques.