Many adolescents engage in unhealthy snacking behavior, and the frequency and amount of unhealthy consumption is increasing further. In this study, we aim to investigate the role that habit strength plays in unhealthy snacking during adolescence and whether self-regulation strategies can overcome habitual snacking. A total of 11,392 adolescents aged 10–17 years from nine European countries completed a cross-sectional survey about healthy eating intentions, snacking habit strength, eating self-regulation strategies, and daily intake of unhealthy snacks. The results showed that habit strength was positively associated with intake of unhealthy snack foods, also when healthy eating intentions were accounted for. Use of self-regulation strategies was negatively associated with unhealthy snacking. The interaction effect of habit strength and use of self-regulation strategies was significant. Strong snacking habits were associated with higher consumption, but this effect could be attenuated by use of temptation-oriented self-regulation strategies. The present study highlights that habit strength is associated with unhealthy snacking already in adolescents. The findings suggest that teaching self-regulation strategies may help adolescents to overcome unhealthy snacking habits.