Fibre Metal Laminates (FMLs) are composite structures that comprise alternating metal layers and fibre-reinforced polymer composites (FRCs) combining their distinct physical-mechanical properties. Traditional FMLs are based on synthetic (carbon, glass and aramid) fibres. However, alternative FMLs based on natural fibre-reinforced composites have been developed to take advantage of available natural resources. A new ecofriendly FML sandwich based on random coir fibre-reinforced epoxy and polyester resin was developed in this research. Mechanical tests revealed that the tensile properties were fully dominated by the aluminium sheets, which were treated with alkali for degreasing and wash primer in order to enhance interfacial bonding. Such treatment efficiently reduced delamination and increased the flexural modulus (~67%). A similar increase in flexural (~22.94%) and impact strength (~99.16%) as well as in skin stress (~20.89%) of the new FMLs proposed was observed owing to the flexural and impact strength of composite cores and better core-layer stress transfer upon the aluminium treatment.