In this paper, the flow characteristics and heat transfer over two equal square cylinders which are placed in tandem arrangement, are investigated numerically. The simulations are performed for a Reynolds number range varying from 1 to 200 and spacing between the cylinders is five widths of the cylinders. The calculations are carried out on a finite volume code for both steady and unsteady incompressible laminar flow in the two dimensional regime. In this study, the instantaneous and mean streamlines and isotherm patterns for different Reynolds numbers are presented. In addition, the effect of Reynolds number on the flow patterns around the cylinders are in detail presented. In addition, the quantities such as pressure and viscous drag coefficients and pressure coefficients are presented.