Rock melon (Cucumis melo L. var. Cantalupensis) is a commercial-type melon with a wide distribution worldwide. Rock melons with larger fruit sizes are more in demand in restaurants, the food processing industry, and large families. In breeding for larger fruits, the increased genetic variability through introgression and recombination is the main factor; then, it can continue to purify before becoming a parental line. The presented study sought to recognize the variability of the open-pollinated population and their performance after selfing. The experiment ran from September 2021 to July 2022 at the Field Experimental Station, Politeknik Negeri Lampung, Indonesia. The experiment consisted of two sub-experiments carried out without experimental design. There was wide variability in both quantitative and qualitative variables in the open-pollinated populations, except fruit flesh color, weight, and sugar content. Population after selfing (S1 population) had more uniform qualitative traits. All the fruits sampled were medium elliptic with netted rinds followed by two-color variants (greenish yellow and green). Also, narrow variability occurred for the traits, fruit diameter, weight, and sugar content, followed by low heritability for the quantitative traits.