Associations between socioeconomic status (SES) and personality, traits and developmental trajectories, have important implications for theory and application. Progress in understanding these associations depends on evaluating how well personality measures function in socioeconomically diverse samples. In the present study, we will use the confirmatory dataset from AIID, a large online study, to address three basic questions about personality and SES. First, we will evaluate the measurement invariance of a common measure of personality, the Big Five Inventory, across indicators of education, income, and occupational prestige. Second, we will estimate previously reported associations between SES indicators and personality in new data to see if they align with past evidence. Third, we will test whether mean-level age trends in personality generalize across levels of SES. The results will have important implications for the validity of past and future research on associations between personality and SES. Additionally, the results will provide insight into differences in personality development trajectories that can inform future work investigating the causal mechanisms between personality and SES.