Coir is one of the most important natural fibers having significant potentiality in structural biocomposites production. The long coir fiber (LCF) and short fibrous chips (CFC) were extracted from the husk of coconut. The dimensions of the CFC were within 1.0-12.5 mm and the LCF were within 2.0 mm. All the fibers and fibrous chips were treated with 5% NaOH (alkali) before the biocomposite manufacturing. Different percentages (8%, 10%, and 12%) of melamine-urea-formaldehyde (MUF) were used to produce the tri-layered medium density composite panels with 12 mm thickness. The mechanical properties (tensile, flexural, and internal bonding strengths) of coir reinforced multilayered composites has been studied for all the produced biocomposites. The morphological, micro-structural, and bonding mechanisms were investigated by Scanning electron microscope and Fourier-transform infrared spectroscopy analysis. Thermal properties of the biocomposites were studied by thermal conductivity, thermogravimetric analysis, and derivative thermogravimetry characterization. The moisture contents of the final composite panels were also investigated in this study. The main objective of this work is to investigate the influences of MUF on treated coir fiber and fibrous chips reinforced tri-layered biocomposites. Beside, a novel sustainable product is developed through reinforcing the fibrous chip with coir fiber in terms of multilayered biocomposite panels.