This paper describes a full-scale experimental program to investigate the structural behavior of insulated concrete sandwich wall panels (SWPs). Main test variables are types of insulation and the number of glass fiber reinforced polymer (GFRP) shear grids. Expanded polystyrene (EPS) and extruded polystyrene (XPS) with the same thickness of 100 mm and Vacuum Insulation panel(VIP) with the thickness of 60 mm are used to satisfy the building insulation requirement in Korea. Various number of GFRP shear grids are used to examine the degree of composite action of two concrete wythes. Each test result is compared with a fully-composite wall panel specimen, which has solid concrete core between concrete wythes. Fifteen SWPs were tested under displacement control subjected to four point concentrated loads. According to the test results, the specimens with EPS exhibit an enhanced load-displacement behavior in comparison with the specimens with XPS because of the relatively high surface roughness of EPS form. Most of specimen failed in the loss of shear-frictional capacity between concrete and insulation followed by rupture of GFRP shear grids. The specimen reinforced with four GFRP shear grids along the shear spans, however, exhibited a full composite behavior up to flexural failure. Based on the test results, the SWPs reinforced with GFRP grids as shear connectors hold an enhanced flexural capacity by developing a high degree of composite action.