Composites from recycled polyethylene and kapok fibers were prepared using untreated and plasma-treated fibers. Flow properties, mechanical properties and fracture morphology were analyzed in order to evaluate the effects of cold plasma treatment on kapok fibers to improve interfacial bonding between fibers and matrix. Melt flow rate (MFR) measurements indicated a reduction in flow rate of the polymer with the addition of kapok fibers. Storage modulus increased with fiber addition and this effect was more significant when plasma-treated fibers were used. Tan delta obtained from viscoelastic characterization also suggested improvements in fiber/matrix interface as a result of plasma treatment. Addition of kapok fibers to polyethylene produced a reduction in onset decomposition temperature determined from thermogravimetry curve. However, the decrease in temperature observed does not limit composite processing. Furthermore, the degree of crystallinity of polyethylene increased with the addition of untreated fibers and reduced when plasma treated fibers were added. Morphological analysis of failure surface by Field Emission Gun Scanning Electron Microscopy (FEGSEM) suggest that fiber/matrix adhesion was clearly improved when plasma treated fibers were used. Thus, the oxygen cold plasma treatment proved to be an effective non-polluting approach to enhance matrix/fiber adhesion in polyethylene/kapok fiber composites, as opposed to chemical treatments. [GRAPHICS] .