ABSTRACT. The effect of Passiflora incarnata's extract (PE) on gonadal maturation in young tilapia (Oreochromis sp.) was evaluated by administering feed supplemented with PE during the first 90 days immediately after yolk sac assimilation. One hundred and fifty fishes with 0.01 ± 0.003 g average body weight were randomly distributed in ten tanks with the following duplicated treatments: commercial feed (NAT), NAT with 60 mg kg -1 of 17-MT (MET), and NAT supplemented with 31.10 mg, 62.30 mg and 124.60 mg of PE g -1 (P1, P2, P3 respectively). There were no significant differences (P > 0.05) in the average body weight or in the male-female sex ratio between the experimental treatments (P1, P2, P3) and the control (NAT). Statistical differences in the gonadosomatic index (GSI) and the percentage distribution of gonadal maturation stages (PDGMS) were observed in females of P2 and P3. With respect to the females of NAT, the treatments P2 and P3 presented a lower GSI and a lower percentage of females in stage III (GSI: 1.11 ± 0.88, 1.04 ± 0.99 and 1.71 ± 0.72; PDGMS: 45, 30 and 80%, respectively). No significant differences in GSI or PDGMS were observed in the males. The results suggest that the observed differences in GSI and PDGMS in females are unrelated to antinutritional effects. Instead, these differences could be due to a possible antiestrogenic effect attributed to the possible anti-aromatase action of some of its compounds. Future research focusing on the use of PE for reproductive control in tilapia is suggested.