In this research, the reinforcing effect of fillers including canola stalk, paulownia and nanoclay, in polypropylene (PP) has been investigated. In the sample preparation, 50 wt.% of lignocellulosic materials and 0, 3 and 5 wt.% of nanoclay particles were used. The results showed that while flexural and tensile properties were moderately enhanced by the addition of nanoclay in the matrix, notched Izod impact strengths decreased dramatically. However, with increase in the nanoclay content (5 wt.%), the flexural and tensile properties decreased considerably. The mechanical properties of composites filled with paulownia are generally greater than canola stalk composites, due to the higher aspect ratio. The thickness swelling and water absorption of the composites significantly decreased with the increase in nanoclay loading. Except tensile modulus, the differences between the type of fibrous materials and nanoclay contents had significant influence on physico-mechanical properties. Morphologies of the composites were analyzed using transmission electron microscopy (TEM) and X-ray diffraction (XRD), and the results showed increased d-spacing of clay layers indicating enhanced compatibility among PP, clay and lignocellulosic material. TEM micrographs also confirmed that the composites containing 3 wt.% nanoclay had uniform dispersion and distribution of clay layers in the polymer matrix.