Purpose: The purpose of this study is to apply Buongiorno’s two phase model to analyse double diffusion natural convection in a square enclosure filled with nanofluids. Design/methodology/approach: A computational code based on the SIMPLE algorithm and finite volume method is used to solve the non-dimensional governing equations. Findings: The nanoparticle plays a crucial role when thermal and solutal buoyancy forces are equal and opposing. Originality/value: This is the first paper to apply Buongiorno’s two phase model for double diffusion natural convection in enclosures filled with nanofluids. © 2019, Emerald Publishing Limited.