In this study, three pea varieties (Pisum sativum), including one field pea variety ‘Dodoni’, and two varieties of garden peas ‘Early Onward’ and ‘Rondo’, were irradiated with 100 Gy gamma rays. The irradiated seeds were then cultivated in the experimental field of the Plant Breeding and Agricultural Experimentation Laboratory of the Agricultural University of Athens, in the period of 2021–2022, affording them the chance to reveal their full potential under natural environmental conditions. The M1 generation plants were compared to non-irradiated plants in terms of their agro-morphological traits. The results indicate a statistically significant difference on several traits: plant height, plant weight, dry biomass, pod length, and the number of seeds per pod. On the other hand, no significant difference was detected in: plant growth rate, the number of shoots and leaves per plant, pods and seed yield per plant, and 1000-seed weight. However, the three pea varieties did not seem to respond in the same way. The M1 generation plants of the two garden pea varieties (‘Early Onward’ and ‘Rondo’) showed a shorter plant height and pod length than their corresponding non-irradiated plants. Likewise, the number of seeds per pod for both ‘Early Onward’ and ‘Dodoni’ was lower for the mutant plants than it was for the plants used as the control. In contrast, mutant plants of the ‘Dodoni’ variety indicated a greater plant weight and dry biomass per plant compared to non-irradiated plants. Finally, the correlation found between agronomic traits was the same regardless of the treatment (control and mutant plants). The number of seeds per plant indicated a positive correlation with the pods per plant and plant weight. Similarly, the dry biomass was positively correlated with plant weight, while being negatively correlated with pod length. Thus, the results obtained in the present study clearly indicate that there were differences between seeds irradiated with gamma rays and non-irradiated seeds in terms of their overall performance and various quantitative pea traits, which should to be further investigated in M2 and the following generations. Peas have gathered a significant market interest and demand. Given their narrow genetic base, we employed gamma irradiation technology, which can be effectively integrated with omics technologies in future generations. This study underscores the necessity to explore performance characteristics and integrate them with quality traits. Our findings reveal that each generation exhibits unique attributes, and specifically, provide a valuable foundation for identifying valuable characteristics for future breeding programs.