Doublesex (Dsx) has a conserved function in controlling sexual morphological differences in insects, but our knowledge of its role in regulating sexual behaviour is primarily limited to . Here, we show with the parasitoid wasp that males whose gene had been silenced ( -i) underwent a three-level pheromonal feminization: (i) -i males were no longer able to attract females from a distance, owing to drastically reduced titres of the long-range sex pheromone; (ii) -i males were courted by wild-type males as though they were females, which correlated with a lower abundance of alkenes in their cuticular hydrocarbon (CHC) profiles. Supplementation with realistic amounts of synthetic ( )-9-hentriacontene ( 9C31), the most significantly reduced alkene in -i males, to -i males interrupted courtship by wild-type conspecific males. Supplementation of female CHC profiles with 9C31 reduced courtship and mating attempts by wild-type males. These results prove that 9C31 is crucial for sex discrimination in ; and (iii) -i males were hampered in eliciting female receptivity and thus experienced severely reduced mating success, suggesting that they are unable to produce the to-date unidentified oral aphrodisiac pheromone reported in males. We conclude that Dsx is a multi-level key regulator of pheromone-mediated sexual communication in .