Ctenoplusia agnata (Staudinger) (Lepidoptera: Noctuidae) is a highly destructive polyphagous pest of cotton, maize, soybean, and cruciferous vegetables in East Asia. The effect of various biotic and abiotic factors on the flight performance of C. agnata is crucial for a better understanding of its transregional migration. In this study, the flight performance of C. agnata moths at different ages, temperatures, and relative humidity (RH) levels, was examined by tethering individual moths to computerized flight mills for a 24-h scotophase. The results showed that 1) C. agnata had the capacity for sustained flight and the flight ability was most pronounced in 3-d-old individuals, and then their flight performance decreased significantly as the moth got older. 2) For both sexes, temperature had a significant effect on their flight performance, and the flight activity was most pronounced at 24–28 °C. 3) There was a significant effect of RH on all flight parameters of the tested moths, and the flight activity was most pronounced at RH of 60–75%. 4) For 3-d-old moths under the optimum conditions (24 °C and 75% RH) throughout the 24-h scotophase, the total flight distance reached 69.01 ± 2.13 km (females) and 62.15 ± 2.31 km (males), and the total flight duration reached 14.11 ± 0.79 h (females) and 13.08 ± 0.70 h (males), which suggests that C. agnata has a strong potential to undertake long-distance migration. These findings will be helpful for developing sound forecasting systems of this pest species.