This study was conducted to examine the physicochemical characteristics and perform QTL mapping of genetic factors associated with the lipid content of rice. A rice strain with a high lipid content, “P31-2-2-2-B-B”, was developed from mutants of “Dongjin” created by T-DNA insertion. The lipid content of “P31-2-2-2-B-B” brown rice was 4.42% whereas that of the donor cultivar “Dongjin” was 2.56%. The total fatty acid content of the high-lipid mutant brown rice was 7.82% and that of “Dongjin” was 3.43%. The unsaturated fatty acid composition of the mutant brown rice was 2.73% oleic acid, 2.74% linoleic acid, and 0.34% linolenic acid. In contrast, the fatty acid composition of the donor cultivar “Dongjin” was 1.30% oleic acid and 0.99% linoleic acid. The percentage of unsaturated fatty acid to total fatty acid in the high-lipid mutant was higher (74.3%) than that of “Dongjin” (66.8%). Continuous frequency distribution and transgressive segregation of the lipid content were observed in the F₃ family (seeds) derived from a cross between the high-lipid mutant “P31-2-2-2-B-B” and a tongil-type cultivar “Samgang”. This result implied that the lipid content was a quantitative trait controlled by a polygene. Additionally, the broad sense heritability of lipid content was estimated to be 89.6% based on analysis of the F₃ seeds. A significant QTL, qRLC5, was identified on chromosome 5 with a LOD score of 2.37, and was flanked by 5007 and 5014. Results of the present study should be useful for improving rice nutritional quality through marker-assisted selection.