This study introduces an inventory that assesses coparenting from the perspective of parents and their adolescent offspring. Within two independent samples of families, we examined reliability and validity of the Coparenting Inventory for Parents and Adolescents (CI-PA). We postulated a model that consists of cooperation, conflict, and triangulation as dimensions of coparenting. Our results showed that this three-factor solution, compared to two- or one-factor solutions, fit the data best. Convergence between mothers and fathers was satisfactory, whereas convergence between parents and their adolescent offspring was weaker, but mostly significant. Moreover, the concurrent validity of the CI-PA was supported by high correlations with a conceptually related questionnaire, and discriminant validity by small to moderate correlations with scales assessing parents' marital quality as well as their individual parenting. Concerning criterion validity, the subscales of the CI-PA accounted for 20% of variance of adolescent psychosocial adjustment. Finally, we discuss implications and limitations of our results. [ABSTRACT FROM AUTHOR]