This study investigates the psychometric properties of a well-set form of the Rational-Experiential Inventory (REI) for adolescents (REI-A20). Participants were 746 Iranian high school students (412 males, 334 females), selected through multistage sampling method. After subjecting our data to principal components analysis (PCA) and parallel analysis (PA), we found a two-factor structure corresponding to rational and experiential processing. Both rational and experiential scales of the REI-A20 exhibited good internal consistency. These two factors accounted for 37% of the variance. The fit indices of confirmatory factor analysis (CFA) confirmed the cross-validity of the inventory. Rationality, but not experientiality, was significantly related to better school performance, elaboration, organization, and metacognitive strategies. Males scored significantly higher on rational scale, but there was no difference between females and males in scores on experiential scale. This new inventory has reliable scores, and allows for valid inferences in assessing individual differences in adolescents’ preference for the rational and experiential information-processing styles.