The objective of this study is to conduct a numerical investigation of turbulent natural convection in a 3-D cavity using Finite Volume Method and Staggered Grid. The statistical-averaging process of the mass, momentum and energy governing equations introduces unknown turbulent correlations into the mean flow equations which represent the turbulent transport of momentum, heat and mass, namely Reynolds stress () and heat flux (), which are modelled using k- SST model. The Reynolds-Averaged Navier-stokes (RANS), energy and k- SST turbulent equations are first non-dimensionalized and the resulting equations are discretized using Finite Volume Method. The results showed an efficient and cost effective procedure for solving a turbulent natural convection problem was by use of an optimized staggered grid and the flow domain discretized by use of Finite Volume Method