Concrete Filled Steel Tube (CFST) columns are preferred as compared to conventional Reinforced Concrete (RC), steel columns owing to their higher axial-flexural capacity, ductility, higher usable floor area and faster construction. In the present study, confinement effect of outer steel tube on infilled concrete core for circular and square CFST columns with identical sectional area of steel tube are investigated through nonlinear Finite Element (FE) computational models under pure axial loading. Limited nos. of experiments investigations are carried out on circular and square CFST along with Hollow Steel Tube (HST) columns to validate of FE analysis of these models. Influence of parameters like; geometric shape and slenderness \(\left( \frac{L}{i} \right)\) ratio on confinement effect is studied by developing 24 nos. of FE models. Strength and deformation capacity of CFST and HST columns are obtained in terms of load–displacement and load-strain relationships for both, FE models and experimental test specimens. Though circular CFST column provides better confinement to core concrete vis-à-vis square CFST column, the later yields confinement of the order ~10% higher despite confinement effect is not considered in deriving strength capacity as per Eurocode design stipulations. It has been observed that, confinement effect found to reduce with increase in the slenderness ratio.