Transient double diffusive natural convection in a square cavity is numerically investigated. The enclosure is heated and cooled along the vertical walls with thermal and solutal gradients, the two horizontal walls of the enclosure are adiabatic and impermeable, the Dufour and Soret effects are considered. The governing equations are solved by using control volume method and SIMPLER algorithm. The main focus of this work is to identify the flow regime for thermal and solutal dominated flows. The flow pattern and heat and mass transfer and the effect of various parameters are analyzed (thermal Rayleigh number, Buoyancy ratio, Soret and Dufour coefficients). Comprehensive Nusselt and Sherwood numbers data are presented as functions of the governing parameters. The results showed that both heat and mass transfer increased in the presence of Dufour coefficient, and the Soret coefficient had great effect on the flow structure.