Fiber-reinforced polymer (FRP)-concrete-steel double skin tubular columns (DSTCs) also known as hybrid DSTCs are a composite column made of an outer FRP tube, an inner steel tube and concrete filled in between. Combining these three materials provides several advantages not found in the traditional columns due their unique properties, such as; high ductility, high strength to weight ratio and good corrosion resistance. In this study a total of 18 DSTCs were manufactured with high strength concrete and have been experimentally tested under axial compression. All specimens were cylindrical with a diameter of 152 mm and height of 305 mm. The test parameters examined by this research were FRP tube thickness and cross-sectional shape of the inner steel tube. The results show that an increase in the FRP tube thickness leads to an increase in the maximum load capacity of the DSTC where this effect is more noticeable as the diameter of the steel tube decreases. It was also observed that the effect of the cross-sectional shape of the inner steel tube on axial load capacity is dependent on the size of the steel tube.