Body odors convey information about the individuals, but the mechanisms are not fully understood yet. As far as human reproduction is concerned, molecules that are produced in sexually dimorphic amounts could be possible chemosignals. 3-hydroxy-3-methylhexanoic acid (HMHA) is one of them—more typical of men. Here, we investigated the possibility that the perception of gender and attractiveness in human faces could be implicitly influenced by this compound. Clearly feminine, ambiguous and clearly masculine faces were primed with an odor of HMHA, a control odor or air. Based on 100-ms face presentation, 40 raters had to identify the face's gender as quickly as possible and provide attractiveness evaluations. 3-hydroxy-3-methylhexanoic acid tended to be perceived as less pleasant and induced lower sniff duration in women compared with men. As to the effects of HMHA on face perception (vs. control conditions), we found that gender identification and the associated response time were unaffected by HMHA. Attractiveness of the faces, however, increased in presence of HMHA, but not in a sex-specific manner and only for unattractive faces with ambiguous gender. In sum, this study found no evidence in favor of a possible role of this sexually dimorphic compound in intrasexual competition nor in intersexual attraction.