The effects of nanoclay content were investigated vs. the mechanical, thermal, and morphological characteristics of a nanocomposite made from poplar wood flour and polypropylene. The wood flour, polypropylene, nanoclay, and the maleic anhydride grafted polypropylene (MAPP) were mixed in an extruder, and the test specimens were made via injection casting. Then, the mechanical and thermal properties were examined. The results showed that the tensile strength, flexural strength, and flexural modulus were improved when the wood flour content increased from 40% to 50%. Additionally, increasing the wood flour content from 40% to 60% enhanced the tensile modulus. The addition of nanoclay at dosages up to 2 wt% enhanced the tensile strength and the tensile modulus, whereas these properties were degraded with the addition of nanoclay at up to 4 wt%. The tensile strength and flexural modulus improved when the nanoclay content increased up to 4 wt%. The crystallinity enthalpy decreased when the wood flour content increased.