This article presents the preliminary data of the development of a Junior version of the Spanish NEO PI-R (JS NEO), suitable for teenagers from 12 to 17 years of age. From the 240 original English items, 92 were modified or reworded to some degree to make the vocabulary adequate for this age group. The psychometric properties of the JS NEO were investigated in a sample of 2,505 adolescents. Results showed that the adult NEO PI-R factor structure was replicated in the junior version of the inventory. Internal consistency and temporal stability reliabilities of the scales were adequate for most scales. Furthermore, the cross-form correlations between the junior (JS NEO) and the adult (NEO PI-R) scales indicated satisfactory construct validity of the junior version of the inventory.