In order to evaluate the reliability of using bottle gourd (Lagenaria siceraria (Molina) Standl.) pollen to produce seedless watermelon, the fruit set rate and qualities of fruits obtained via parthenocarpy using the watermelon cultivar ‘Fujihikari TR’ were investigated. Pollen from several cultivars of bottle gourd was tested. To verify that pollen from another genus can be used universally to produce seedless fruit, the fruit set and fruit quality of several watermelon cultivars were measured in experiments using pollen from different bottle gourd cultivars. The timing of flowering and production of male bottle gourd flowers were investigated to identify the best combination for pollinating watermelon with bottle gourd pollen in the early spring season. Seedless watermelon could be produced from the pollen of several cultivars of bottle gourd. The watermelon fruit set rate after pollination with bottle gourd pollen was lower than that using watermelon pollen. The watermelon fruit set rate after pollination with L. siceraria var. hispida pollen was higher than that of L. sciceraria var. gourda pollen. There were no differences in the characteristics of seedless fruit produced by pollinating with different bottle gourd cultivars. Bottle gourd pollen could produce seedless fruit in several watermelon cultivars. Several common traits were evident in seedless watermelon fruit. Seedless fruit tended to be oblong, have hollow hearts, and have a higher °Brix compared with normal fruit. Seedless fruit had only empty seeds, and the number of empty brown seeds differed among watermelon cultivars. There were varietal differences in the male flower traits of bottle gourds. Seedless watermelon production can be facilitated by carefully evaluating the timing of anthesis in male bottle gourd flowers.