<p>This study examined the longitudinal, reciprocal relationships between the Big Five personality traits and self-esteem using 16 waves of annual data from a large, nationally representative Dutch household panel collected between 2008 and 2024 (<i>N</i> = 9,249). Self-esteem and Big Five traits were assessed using the 10-item Rosenberg Self-Esteem Scale and the 50-item International Personality Item Pool, respectively. Employing multilevel cross-lagged modeling, within- and between-person variances were partitioned to isolate how intra-individual changes in traits and self-esteem predict future changes in each other, controlling for stable individual differences. Results indicated statistically significant bidirectional within-person effects across all five traits and self-esteem, with moderate effect sizes. Changes in emotional stability were the strongest predictor of subsequent changes in self-esteem, and changes in self-esteem predicted later changes in openness more strongly than in other traits. Between-person analyses confirmed stable trait-level associations between all traits and self-esteem. Age and gender were included as between-person covariates, replicating established demographic patterns documented in prior research. This study demonstrates that within-person fluctuations in self-esteem and the Big Five traits are dynamically and reciprocally linked over time, indicating that self-evaluations and trait expressions co-develop in the long term.</p>