Previous research has demonstrated a strong positive relationship between job and life satisfaction. Traditionally, this relationship has been explained in terms of a spillover model, wherein job experiences spill over onto life, and vice versa. This study directly tests a different explanation for this relationship: personality traits that influence both job and life satisfaction. In a longitudinal test with multisource data, three typologies, which were shown by past research to be linked to both job and life satisfaction, were examined: Big Five, positive and negative affectivity, and core self-evaluations. One hundred and fifty-three university employees working in a diverse set of occupations were surveyed twice, with a six month time interval; the first survey also included a second questionnaire to be completed by a 'significant other.' Analyses of concurrent and prospective zero-order and partial correlations, as well as structural equation modeling, supported the hypothesized confounding role of all three typologies, especially core self-evaluations. Though controlling for personality reduced the magnitude of the job - life satisfaction relationship, it did not entirely eliminate it. Overall, the results suggest the presence of both dispositional and environmental factors in job and life satisfaction. Finally, implications for organizational practice and theory development are discussed.