Abstract Coconut mesocarp fiber (CMF) is a by-product of the coconut industry; it was milled to produce coconut mesocarp particles (CMP). The main elements identified in CMP samples were C and O, which represent 96.75%. The CMP were mixed with a polylactic acid (PLA) matrix by extrusion. The mechanical, thermal, structural, and morphological properties of four biocomposites with 0, 2, 5, and 8 wt% CMP (CMP0, CMP2, CMP5, and CMP8, respectively) were determined. The biocomposites showed a decrease in tensile strength, elongation at break, and elastic modulus values as the CMP content increased, except for CMP5, which showed a higher elastic modulus than the PLA matrix. The thermal analysis showed that the biocomposites presented better thermal stability than the PLA matrix. CMP2 and CMP5 had rough surfaces, while CMP8 had weaker fracture zones. CMF (CMF byproduct product industry CMP. . (CMP) O 9675 96 75 96.75% (PLA extrusion mechanical structural 0 2 5 wt CMP0, CMP0 (CMP0 respectively determined strength break increased surfaces zones (CMP 967 9 7 96.75 96.7 96.