Induced mutagenesis through gamma radiation generates structural and chemical changes in plants. This study evaluated the morphological and nutritional variability of natal grass [Melinis repens (Willd.) Zizka] plants produced from seed irradiated with gamma radiation. Natal grass seed was collected from wild populations in the state of Chihuahua, Mexico. The seed was exposed to a source of Co60. The radiation doses were: 0, 10, 50, 100, 150, 200, 250, 300 and 350 Gray (Gy). Sixty-six first generation mutant genotypes (M1), produced from irradiated seed, and nine non-mutant genotypes (M0), developed from non-irradiated seed (0 Gy), were evaluated. For the morphological characterization, 18 variables were measured on the plants when they were at the reproductive stage. The nutritional analysis was performed on the M0, as well as on a group of plants from the M1, which resulted morphologically different (p <0.005) from the rest. The differenced M1 plants were classified as promising mutant genotypes (M1p). Results showed that variability was induced in the M1p. These individuals presented morphological differences in leaf weight-tillering weight ratio and foliage height, compared to the rest of the plants (p <0.001). The M1p 250-10 genotype presented the highest (p <0.001) crude protein and the lowest (p <0.001) lignin contents. Gamma radiation in the seed of natal grass induced morphological and nutritional variability. With that, promising mutant genotypes, with desirable morphological and nutritional attributes, were identified.