[Objectives]  To determine the effect of age and infection by the nematode Deladenus siricidicola Bedding on the flight capacity of Sirex noctilio. [Methods]  Insects were obtained from the trunks of Pinus sylvestris var. mongolica Litv. in Hegang Heilongjiang province and reared indoors under laboratory conditions. The flight capacity of adult S. noctilio of 1, 2, 3, 4, 5, 6, 7 and 8 days of age was tested for 12 h in a Jiaduo flight mill system. Total flight distance, total flight duration and average flight speed were recorded. [Results]  Total flight distance and total flight duration declined with age. There was a significant difference in average flight speed among females of ages, and average flight speed gradually declined with age. However, there was no significant difference in average flight speed among males of different ages. The flight capacity of the sexes differed; females generally had a longer total flight distance and total flight duration than males but there was no significant difference between the sexes in average flight speed. Total flight distance was affected by a significant interaction between sex and age. Nematode infection had no obvious influence on the flight capacity of S. noctilio. [Conclusion]  The flight capacity of S. noctilio decreases with age and the females have greater flight capacity than males. Nematode infection appears to have no significant effect on flight capacity.