Constraints are reported for the low productivity and quality of onion seed production in Upper Egypt. Therefore, a field experiment was conducted to study the influence of planting date and genotypes on yield and quality of onion seed production under Upper Egypt conditions where high average day /night-time of temperatures (27.4 ̊C and 11.2 ̊C) for two seasons. The results revealed significant interactions between planting date and genotypes on seed yield/plant in both seasons and the number of umbel/plant in the 2^nd season. The highest seed yield (442.25 kg/fed^-1) was recorded from Giza 20 planted in Early November sowing. Planted onion bulb set early- November increased seed yield (by 9.6% -17.9 % kg/fed) than grown early December. As a result, Giza 20 cultivar in early November in the current study area and other similar agroecology areas could be suggested to produce a better seed yield of onion. A principal component analysis was performed to interpret the distance between the genotypes. The average inter-cluster distance was found maximum (154.15) between G1 (Sabeeni) and G4 (Giza 20). The differences between the behavior of the seven studied traits in Giza 6 and Giza Red (Group I) are very weak, while for Sabeeni (Group III) and Shandaweel 1 (Group IV), the extent of the differences between the average traits reaches 26.5 % and 29.2% in 1^st and 2^nd planting dates under the conditions of Upper Egypt, thus considered 2 groups. The inter-seasonal and intra- seasonal fluctuation in both climatic parameters greatly affected the studied onion traits.