The Eastern Grass-veneer Agriphila aeneociliella (Eversmann) (Lepidoptera: Crambidae) is a serious stem-feeding pest of wheat crops that has become established in China in recent years. A better understanding of the mating strategy and reproductive performance of A. aeneociliella could improve integrated pest management programmes against this newly established species by disturbing its behaviour and reducing its reproduction potential. Based on ethological and reproductive biological approaches, the mating and reproductive performances of A. aeneociliella were investigated. Unlike the common nocturnal lepidopterans, the mating rhythm of A. aeneociliella moths showed a marked diurnal pattern. The female courtship rhythm and the mating rhythm reached peaks within the first 2 h after the onset of photocycle. The mating success rate of monogamous pairs was 55.6%, whereas the male-biased sex ratio (2♂:1♀) increased the mating rate (72.2%) and the female-biased ratio (1♂:3♀) led to the lowest mating rate (27.8%). Both females and males were able to mate twice. The duration of copulation decreased substantially with male mating frequency, whereas, when a previously mated female was paired with a virgin male, fecundity significantly increased. Monogamous couples who mated only once in their lives have the highest hatchability (97.13 ± 0.49%).