Social neurodevelopmental imbalance models posit that peer presence causes heightened adolescent risk-taking particularly during early adolescence. Evolutionary theory suggests that these effects would be most pronounced in males. However, the small but growing number of experimental studies on peer presence effects in adolescent risky decision-making showed mixed findings, and the vast majority of such studies did not test for the above-described gender and adolescent phase moderation effects. Moreover, most of those studies did not assess the criterion validity of the employed risky decision-making tasks. The current study was designed to investigate the abovementioned hypotheses among a sample of 327 ethnically-diverse Dutch early and mid-adolescents (49.80% female; Mage = 13.61). No main effect of peer presence on the employed risky-decision making task (i.e., the stoplight game) was found. However, the results showed a gender by peer presence moderation effect. Namely, whereas boys and girls engaged in equal levels of risks when they completed the stoplight game alone, boys engaged in more risk-taking than girls when they completed this task together with two same-sex peers. In contrast, adolescent phase did not moderate peer presence effects on risk-taking. Finally, the results showed that performance on the stoplight game predicted self-reported real-world risky traffic behavior, alcohol use and delinquency. Taken together, using a validated task, the present findings demonstrate that individual differences (i.e., gender) can determine whether the social environment (i.e., peer presence) affect risk-taking in early- and mid-adolescents. The finding that performance on a laboratory risky decision-making task can perhaps help identify adolescents that are vulnerable to diverse types of heightened risk behaviors is an important finding for science as well as prevention and intervention efforts.