The band structure of InSb thin films with 〈1 0 0〉 surface orientation is calculated using the empirical pseudopotential method (EPM) to evaluate the performance of nanoscale devices using a InSb substrate. Contrary to the predictions by simple effective mass approximation methods (EMA), our calculation reveals that the Γ valley is still the lowest lying conduction valley. Based on EPM calculations, we obtained the important electronic structure and transport parameters, such as effective mass and valley energy minimum, of InSb thin film as a function of the film thickness. Our calculations reveal that the 'effective mass' of Γ-valley electrons increases with the scaling down of the film thickness. We also provide an assessment of nanoscale InSb thin film devices using a non-equilibrium Green's function under the effective mass framework in the ballistic regime.