The flow around bluff bodies like cylinders with circular and square cross section is observed in many engineering applications such as adjacent skyscrapers, groups of chimney stacks, tubes bundles in heat exchangers, suspended bridges etc. For these configurations, the flow interference has an essential role for several changes in the characteristics of the flow. Thus, the dynamic interaction between the structure and the fluid is one of the most fascinating problems in engineering mechanics. Some studies including both numerical and experimental investigations have been conducted for the ?ow over square cylinders in tandem and side-by-side arrangements, but the turbulent flow over staggered square cylinders is not reported yet. In this research the flow around two staggered square cylinders is studied experimentally by using the wind tunnel and smoke tunnel. Experiments were performed in Isfahan University of Technology labs. The distance between the centers of the models is varied between 2D to 5D, where D is cylinder side, and the staggered angle is varied between zero to 90 degree. The pressure coefficients (Cp) on the models’ faces are measured via sensors which are placed on theirs’ faces. The flow patterns around two cylinders are investigated by smoke visualization for different gap spacing and staggered angles. Measuring velocity field and turbulence quantities around two square cylinders are carried out using hot wire anemometry for various gap distances. Six major regimes are distinguished according to the gap spacing between cylinders and staggered angles, that is, shear layer reattachment, induced separation, vortex impingement, vortex pairing and enveloping (VPE), vortex pairing, splitting and enveloping (VPSE), synchronized vortex shedding (SVS) for staggered arrangement. Based on the results of visualization, the width of wake, the separation angle and length of the shear layer have been determined. Pressure coefficients on the surfaces of cylinders have been measured by pressure sensors in wind tunnel, and the drag coefficients have been calculated by the pressure coefficients. Frequency analysis have been performed for staggered angles of 0 to 90 degrees for the distance between the cylinders of 2 to 5, using a hot wire anemometer in a wind tunnel. The results of this study indicate that the space between cylinders and staggered angles are main factors to influence the flow patterns, velocity, pressure and Strouhal number. The results also show that two different dominant frequency are occurred for staggered arrangement for some gap spacing and staggered angles Key Words : Square Cylinder, Staggered Arrangement, Wind Tunnel, Smoke Tunnel, Hot wire, Flow Pattern, Pressure Coefficient, Strouhal Number