The massive invasion and proliferation of Sargassum algae on Caribbean beaches and coasts in recent years is threatening people's livelihoods, climate-sensitive areas and local ecosystems. The aim of this study was to assess the feasibility of manufacturing multi-layer composite particleboard using pelagic Sargassum as filler, coconut leaf sheaths as reinforcement and polylactic acid (PLA) as natural binder. The composites were subjected to three-point bending, density, porosity, morphology and biodegradability tests to assess the effect of number of layers, binder content and applied pressure during hot-pressing process on composite performance. The results show that weight loss after 15 days of biodegradation varies from 8.33 to 66.22%, with the greatest biodegradation observed on the composite consisting of a single layer of coconut leaf sheath. The stress-strain curve of the composite shows a ductile behavior of the materials, and only the composite composed of a 3-layers of coconut leaf sheaths and 10% by weight of PLA, pressed at 5 MPa, achieves the minimum flexural modulus of rupture of 18 MPa, as recommended by the Brazilian standard. Although the multi-layer composite has acceptable mechanical performance, appropriate treatment should be applied to Sargassum seaweed to control its water resistance.