Abstract: The mutagenic effect of colchicine to improve leaf and seed yield in two varieties of sesame (Sesamum indicum L. var. Yandev and Ex-Sudan) was investigated. Seeds of the two sesame varieties were presoaked in five different colchicine concentrations (0.1, 0.5, 1.0, 1.5 and 0.0 mM as control). The seeds were planted in a completely randomized block design for two mutant generations (M1 and M2). The M2 mutants were characterized on the basis of morphological traits such as height at maturity, anthesis period, number of leaves/plant, leaf area, internodes length, number of capsules/plant, length of capsules, number of seeds/capsule and 1000 seeds weights. The results obtained revealed highly significant difference (p≤0.01) in the morphological traits of the mutants when compared with the controls, except in the number of seeds where the effect of the mutagen is significant (p≤0.05). More so, with the exception of internodes length and 1000 seeds weight, the leaf yield parameters of the M2 mutants were found to correlate significantly with the seed yield. Similarly, colchicine was found to induce changes in the chlorophylls and carotenoids bio-syntheses among the M2 mutants, leading to the formation of five forms of chimeras as chlorinas, xanthas, striatas, virescents and lustescents. It was therefore, inferred that, colchicine-induce mutants were characterized as early flowering with tall stature having larger leaves and which produced large number of capsules with numerous seeds. The improvement of the mutants’ traits is concentration dependent, increases with decrease in colchicine concentration. Thus, we therefore suggested that, 0.1 mM concentration should be employed in improving sesame growth and yield related traits.