Country and ethnic group differences on adjustment have been demonstrated numerous times, and the source of these differences has been typically interpreted as cultural. We report two studies in which country (Study 1) and ethnic group (Study 2) differences on depression, anxiety, optimism versus pessimism, well-being, and self-esteem are mediated by dispositional traits. These findings provide an alternative explanation for previously reported country and ethnic group differences on these variables and encourage researchers to consider multiple sources, including traits, in their models and studies.