The progress in establishing new classes of biocomposites has led to potential applications in the automotive, aerospace, and construction industries because of their life cycle properties, low cost, lightweight, non-abrasive and moderate mechanical strength. The heterogeneity of natural fibers plays an important role in the fiber–matrix adhesion, therefore affecting the mechanical performance and the durability of the composites. This work has described the manufacturing, characterisation and testing of hybrid composites reinforced with sisal fibers and silica nanoparticles. A full factorial design was performed to identify the effects of fiber treatment, fiber orientation and nanosilica inclusion factors on the physical and mechanical properties of hybrid composites. Composites made with unidirectional untreated fibers and silica nanoparticles (2 wt%) provided not only higher strength, stiffness, and impact resistance, but also lower overall porosity. POLYM. COMPOS., 2016.