Random amplified polymorphic DNA (RAPD), inter simple sequence repeat (ISSR), and UPOV phenotype markers were used to study the DNA polymorphism in gamma-ray induced morphological mutants of Celosia argentea var. plumosa Hungarian variety ‘Arrabona.‘ In the experiments, the study determined the radio sensitivity and the genetic diversity of gamma radiation of C. argentea var. plumosa ‘Arrabona.‘ Seeds of C. argentea var. plumosa ‘Arrabona‘ were irradiated with gamma rays to increase their genetic diversity. The irradiation doses consisted of 0, 75, 150, 300, 450, and 600 Grays (Gy). The germination percentage, survival rate, and phenotype of irradiated plantlets underwent evaluation in the first (M1) and second (M2) generations. The investigation of genetic diversity used the ISSR and RAPD primers. Based on the results, the first-generation genetic distance increased as the doses increased. But the trend changed considerably through the generation due to the low condition and fertility of the high doses of gamma-irradiated plants. These individuals did not show at the next mutant generation, changing the population gene pool. In addition, open pollination has also changed genetic diversity. The RAPD and ISSR primers proved proper to evaluate the genetic diversity, nonetheless fewer direct connection occurred between the appearance and the used RAPD or ISSR markers. The LD50 dose between 150 and 300 Gray treatments and the radiation between 300450 Gray induced the median growth reduction in the mutant ‘Arrabona‘ population. Based on these results, the study concluded that both UPOV-based phenotyping and molecular marker analysis revealed appropriate for determining genetic divergence, but detecting greater genetic distance resulted in molecular markers.