The diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a notorious insect pest of cruciferous crops worldwide. Attract‐and‐kill strategies to manage the DBM based on insect pheromone and plant volatile semiochemicals have been explored and partially applied in the field. However, little is known about whether the attractant effects of insect pheromone and host plant volatile semiochemicals on insects are affected by insect age or volatile concentrations. Therefore, we examined the electroantennogram (EAG) responses of both DBM males and females varying in age and body size to a range of concentrations of seven host plant volatiles and two main female sex pheromone components. Our results showed that DBM age had no influence on EAG responses to trans‐2‐Hexenal, trans‐2‐Hexenol, Heptanal, cis‐3‐Hexen‐1‐ol and Z11‐16:Ald and significantly influenced the EAG responses to Z11‐16:Ac and three isothiocyanates. Age and sex had interaction effects on EAG responses of DBMs to some tested semiochemicals. DBM females had significantly stronger responses than males to all tested plant volatiles, and values were enhanced with increasing concentrations. Moreover, the degree of enhancement of EAG responses in females was larger than that in males for trans‐2‐Hexenal, trans‐2‐Hexenol, cis‐3‐Hexen‐1‐ol, 2‐Phenylethyl isothiocyanate and Methyl isothiocyanate treatments. Body size seemed to have no influence on EAG responses. Our results might provide a theoretical basis for optimizing attract‐and‐kill strategies for insect pests.