A systematic study has been done on the electronic and magnetic properties of metamagnetic Ni-Mn-In Heusler alloy with compositional and structural (anti-site) disorder at high temperature austenite phase. The electronic structure calculation shows an increasing Mn-Ni hybridization which occurs due to the decrease in Mn-Ni bond length as the system approaches martensite phase. The results obtained from magnetic moment calculations follow a similar trend to the previous experimental and theoretical results. The magnetic coupling parameters, Jij, obtained from the ab initio calculation explains the presence of competing ferromagnetic (FM) and antiferromagnetic (AFM) interactions in the system and the dominating AFM interactions nearer to the martensite phase.