Mungbean [Vigna radiata (L.) R. Wilczek] is an agro‐economically important legume crop of Thailand. In recent years, mungbean has been gaining attention and popularity from consumers and industries for its dense nutrients. Although farmers, consumers, and processors prefer large‐seeded mungbeans, all mungbean cultivars available in Thailand are medium‐seeded. Therefore, a need was felt to develop new mungbean cultivars with large seed size that would fulfill the needs of farmers, consumers, and processors. In this study, we report the development of two new mungbean cultivars: ‘KUML4’ (Reg. no. CV‐354, PI 703288) and ‘KUML8’ (Reg. no. CV‐355, PI 703289). These cultivars were developed by pedigree and bulk‐selection methods. Standard yield trials revealed that KUML4 gave seed yields (SDY) of 1444.75 and 1316.38 kg ha−1, respectively, which was on par with check cultivars. The seed of KUML4 and KUML8 was larger than all of the check cultivars; their 100‐seed weights were 7.25 and 7.84 g, respectively, compared with 6.58 g, the mean of the check cultivars. Further, the genotype main effect plus genotype‐by‐environment analysis showed that KUML4 had good yield stability for its SDY. The yield trials under farmer fields and practices revealed that KUML4 gave SDY similar to the best check cultivar, ‘Chai Nat 3’ (CN3), whereas KUML8 gave a lower yield than CN3. The yield gap between the experimental research station and farmer field/practice was about 47%. In conclusion, KUML4 and KUML8 have shown high yield, large seed size, and early and uniform maturity.