<p>The study aimed to identify optimal ethyl methanesulphonate (EMS) dose and soaking duration to induce genetic variation in selected founder tef (<i>Eragrostis tef</i> [Zucc.] Trotter) cultivars. Study conducted using a 3 × 5 × 4 factorial experiment with seeds from three founder cultivars (Emerson, Highveld and Ivory), five EMS doses (0.00%, 0.50%, 1.00%, 1.50% and 2.50%) and four soaking durations (1, 2, 4 and 8&#xa0;h). Data were collected on M₁ to M₃ derivatives on the following parameters: germination percentage, days to 50% emergence, seedling survival, seedling height, root length and number of tillers. Ideal EMS dose of 2.11% and 4-hour soaking duration were discerned at M1 and used in large-scale mutagenesis, enabling the development of M₂ and M₃ generations. There were significant (<i>p</i> &lt; 0.001) interactions of cultivar × dose, cultivar × soaking duration, and dose × soaking duration for germination percentage, days to 50% emergence, seedling survival percentage and shoot height. EMS dose had a highly significant (<i>p</i> &lt; 0.001) effect on all assessed traits except root length. Study identified following EMS mutagenesis conditions as ideal for tested founder cultivars: 1.67% at 4-hours soaking duration Emerson, 2.97% at 4-hours soaking duration Highveld and 1.67% at 4-hours soaking duration Ivory.</p>