Jealousy responses to potential mating rivals are stronger when those rivals display cues indicating higher mate quality. One such cue is vocal femininity in women's voices, with higher-pitched voices eliciting greater jealousy responses. However, cues to mate quality are not evaluated in isolation. The steroid androstadienone (AND) is a putative sex pheromone that makes women perceive ambiguous stimuli as more masculine. We hypothesized that AND would decrease the association between vocal femininity and jealousy, as it induces a perceptual bias that is incongruent with the femininity of the voice. In a double-blind, within-subjects study, 70 heterosexual Chinese women in the periovulatory phase of their menstrual cycle came to the laboratory twice to listen to pairs of voices manipulated to sound more or less feminine. For each pair, the participants selected the voice that would elicit more jealousy if flirting with their partner. The results showed that vocal femininity provoked jealousy under control conditions, replicating previous findings. However, this effect was weakened when women were exposed to AND, suggesting that AND disrupts sensitivity to vocal cues about mate quality in same-sex competition. These results demonstrate a contextual modulation of jealousy responses to sexual rivals.