The present study addresses a fundamental yet largely neglected question about personality development: To what extent are changes in parent personality traits associated with changes in their child's personality traits? Numerous developmental processes suggest that parent and child personality might have transactional associations over time, contributing to their codevelopment. This codevelopment may be homotypic (e.g., associations between changes in parent and child conscientiousness) and heterotypic (e.g., associations between changes in parent conscientiousness and changes in child extraversion). In addition to investigating the extent to which parent and child personality codevelops, we also investigated the extent to which parental (mother and father) personality codevelops. We tested these ideas using bivariate growth curve models of personality trait assessments from a 17-year longitudinal study of 674 Mexican-origin families. Intercepts of parent and child trait trajectories were generally correlated, but we did not find significant correlations between the slopes, contrary to our expectation of parent-child codevelopment. We found stronger evidence for codevelopment in mom-dad dyads, with significant slope-slope correlations for extraversion, agreeableness, and openness. In almost all cases, the results generalized across child gender, child nativity, and parental age. We discuss the implications of the findings for adolescent personality development. (PsycInfo Database Record (c) 2025 APA, all rights reserved).