This study focused on the myco-fabrication of packaging materials based on biosourced fungal mycelium. The methodology includes evaluating several substrates, focused on wood sawdust, spent coffee grounds, and orange peels with five filamentous strains. The screening steps on solid and liquid agrowaste media, as well as the elemental compositions of the waste substrates, showed that the T. versicolor BS7 strain grown on the mixture of spent coffee grounds and wood sawdust (SCG/Saw) seems to be promising for mycelium-based biocomposites (MBCs) biofabrication. The analysis of the chemical properties indicated that the pH value, nitrogen content, and organic matter content of the obtained MBCs were within the following ranges: 4.67–5.8, 1.05–1.043%, and 27.2–25.5%, respectively. The SEM analysis reveals that the combination of SCG and sawdust induced a well-developed mycelial network contributing to the material’s water absorption (125.73% after 1 h). Also, the obtained MBC exhibits good density (0.580 g cm⁻³), moderate compressive strength of 3.62 ± 0.5 MPa, relatively high strain at failure (57%), and good thermal stability with Tmax of 601.23 °C. The biodegradation percentage for this optimal composition indicates that MBC can easily decompose in the environment. Overall, the MBC derived from SCG/Saw appears to be a promising biomaterial with potential applications in soil amendments.