The present study examined psychological and psychopathological correlates of psychological inflexibility as measured by the Avoidance and Fusion Questionnaire for Youth (AFQ-Y) in two independent samples of nonclinical Dutch adolescents aged between 12 and 18 years (Ns being 184 and 157). Participants completed a survey containing the AFQ-Y and scales assessing mindfulness, thought suppression, self-compassion, self-worth, self-efficacy, and internalizing/externalizing symptoms. In both samples, the AFQ-Y was found to be a reliable measure of psychological inflexibility that correlated in a theoretically meaningful way with other psychological constructs. Most importantly, AFQ-Y scores correlated positively with internalizing and externalizing symptoms, and in most cases, these associations remained significant when controlling for other measures. These findings suggest that psychological inflexibility is an important factor in youth psychopathology that needs to be further investigated in future research.