[Objectives]  To determine the effects of delayed mating on the reproduction of the potato tuber moth Phthorimaea Operculella (Zeller). [Methods]  The effects of delaying the mating of both males and females, or of delaying the mating of either males or females, for different numbers of days, on mating rate, mating duration, fecundity and adult lifespan, were compared under laboratory conditions. [Results]  Irrespective of which sex was prevented from mating, delaying mating for 5 d produced the lowest mating rate. Compared to delaying the mating of females, the effect of delaying the mating of males, or of both sexes, on the mating rate was more obvious. Delayed mating had obvious adverse effects on the hatching rate and the number of eggs laid. Irrespective of which sex was prevented from mating, egg production was highest when mating was delayed for 2 days, and lowest when it was delayed for 5 days. Delaying mating by 5 days resulted in a significant difference in egg production when mating by both sexes had been delayed compared to when mating by females only had been delayed. In addition, the lifespan of both sexes was higher when mating was delayed, and compared to delaying the mating of just one sex, the effect of delaying mating by both sexes on lifespan was more obvious. Males were more susceptible than females to the effects of delayed mating. [Conclusion] Delayed mating has significant adverse effects on the reproduction of potato tuber moths, which suggests that there is some scope for controlling this pest by disrupting mating.