The graft copolymers of pure granular maize starch with acrylamide, methacrylamide, acrylic acid and methacrylonitrile were synthesized using ceric ammonium nitrate as an initiator. The formation of graft copolymer was confirmed by gravimetric measurement, acid hydrolysis and IR spectroscopy. The thermal analysis of the pure granular maize starch and graft copolymers was carried out using thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), differential thermal analysis (DTA) and isothermal analysis. In order to determine the mechanism of decomposition of these polymers, the isothermal analysis was coupled with IR spectroscopy. The activation energies at every stage of decomposition for all the polymer samples were determined from their primary thermograms. The glass transition temperatures (T g ) for pure granular maize starch and all the graft copolymers have been reported. Except starch-graft-acrylic acid, all other graft copolymers showed enhanced thermal stability over pure starch. T g of pure starch was observed as 91 °C. All the graft copolymers showed lower values of T g with a minimum of 57 °C for starch-graft-methacrylonitrile. DTA studies indicated a delayed oxidative degradation of graft copolymers.