Gelatinization temperature of rice starch plays an important role in grain quality. We mapped eight loci responsible for the gelatinization parameters of rice: onset temperature (To), peak temperature (Tp), conclusion temperature (Tc) and enthalpy (ΔH) using a population of 242 recombinant inbred lines (RIL). Eight quantitative trait loci (QTL) were mapped onto the chromosome regions where starch-synthesis related genes are located. The Wx gene (granule-bound starch synthase [GBSS]), and the region of chromosome 11 played major roles in gelatinization trait determination; and other loci were starch-branching enzyme (SBE) genes that modify the two major loci by epistasis. High-level interactions were also detected indicating a trans mode of action of the genes. The genetic basis for these parameters was consistent with the relationship between the thermal properties and the structure of the starch granule. This information can be helpful for the improvement of starch-producing crops, including the improvement of rice grain quality, both for food and industrial uses.