Periodical release of non-viable refrigerated eggs of Riptortus pedestris (Fabricius) has been found to enhance field parasitism level in soybean fields. However, optimum refrigeration conditions required for the eggs in order to preserve its quality to ensure effective level of parasitism for a longer period has been rarely reported. We assessed optimum environment condition for refrigeration of the eggs using three different temperatures (2, 6, and 10℃) and relative humidities (RH) (high, medium and low). Eggs of R. pedestris were refrigerated at nine combinations of temperature and relative humidity for 30 consecutive days. Those eggs were taken out and after 8 days, mated female Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) were individually exposed to the eggs, and their development, emergence, and sex ratio were examined. Number of eggs parasitized was highest (5.9) on eggs stored at 6℃ and high RH. Significantly higher male proportion was recorded in the eggs stored at 10℃. However, RH had no effect on the sex ratio. For both male and female, development time was the least on host eggs stored at 2℃ and high RH. Adult emergence was recorded highest from the eggs stored at 2℃ followed by 6℃ and at high RH. In conclusion, eggs refrigerated below 6℃ at high RH condition maintained better quality of R. pedestris eggs for the parasitization by O. nezarae.