In this paper, we present ab-initio study on the energy configurations, minimum energy path (MEP), and migration energy of neutral indium atom during diffusion in silicon crystal. From the ab-initio calculation of electronic structure, we could figure out the transient atomistic configurations during the indium diffusion in silicon. We found that the lowest-energy structure (Ins + Sii Td) consists of indium sitting on a substitutional site for stabilizing a silicon self-interstitial in a nearby tetrahedral position. The second lowest-energy structure was found to be Ini Td, the interstitial indium at the tetrahedral position. We employed the climbing image nudged elastic band (CINEB) method for estimating the MEP between the two local energy minima and the migration energy of the neutral indium, and obtained the MEP of 0.79 eV.