In this article the authors investigate the extent to which traits reflecting individual differences in personality and affectivity explain or mediate genetic influences on job satisfaction. Using estimates of the dispositional source of job satisfaction according to 2 dispositional frameworks--the five-factor model and positive affectivity-negative affectivity (PA-NA)--and behavioral-genetic estimates of the heritabilities of job satisfaction and the dispositional factors, the authors computed the proportion of genetic variance in job satisfaction that is explained by these trait frameworks. Results indicate that the affectivity model is a stronger mediator of genetic effects on job satisfaction than the five-factor model. PA and NA mediate about 45% of the genetic influences on job satisfaction, whereas the five-factor model mediates approximately 24% of these genetic effects.