The soundness and the performance of castings are significantly affected by generation and accumulation of residual stresses. This has been proven that mechanical properties and residual stresses level of the casting components are affected by thermal gradient across the casting component during cooling and some intrinsic physical properties of the material. In the present work, microstructural development, mechanical properties, residual stress evolution and cooling curves associated with different legs of a mixed–section grid castings have been investigated employing scanning electron microscope, optical microscope, 3D measurement equipment, computerized thermal data acquisition instrument and tensile testing machine. Experimental results show that the accumulated residual stress in circular, triangular and rectangular grid shapes is increasing respectively. From the results it can be seen that there are clear influences of grid’s geometry on the microstructure and mechanical properties. The geometrical stiffness can affect a lot the residual stress level and the casting modulus has a big influence on the microstructure and mechanical properties.