This study drew upon the affective events and mood-congruent cognition theories to help explain how one domain influences the other. Affective events are things that happen to which people react emotionally and state affect is a result of those affective experiences. This study proposed that state affect generated in one domain would spillover and influence mood-congruent experiences in the receiving domain. Through an integration of organizational stressor-strain models (e.g., job-resources demand theory) and positive psychology, this study further proposed that positive events are resource-building and will work to prevent or buffer against strain responses to resource-depleting negative events. Finally, this study explored how individual differences in domain integration and work- and family-role salience moderate the foregoing relationships, particularly because studies investigating these effects have produced mixed results. To address these empirical questions, this study used the daily diary method to examine daily affective spillover effects from work-to-family and from family-to-work in a full-time working sample over the course of two weeks. This method was employed to help bolster confidence about the temporal precedence of work-family affective spillover and employee health and wellbeing outcomes. One-hundred and forty-four participants filled out diary questionnaires three times daily during the work week and one time daily during the weekend. Daily diaries assessed the participants’ exposure to a number of domain-specific affective events, state affect, physical symptoms, and sleep quality. Hierarchical linear modeling was used to test this study’s hypotheses. Overall, the results of this study support affective spillover as the linking pin between the two domains, which has health and wellbeing implications for employees. Specifically, tests of this study’s hypotheses indicated that exposure to affective events throughout the workday was related to state affect at the end of the workday, which then related to the number of valence-congruent affective events within the family domain. Exposure to those family-related affective events was related to corresponding changes in state affect, which not only persisted to the next morning but impacted employee health and wellbeing in terms of psychosomatic complaints. These findings are in line with both the affective events and mood-congruent theories. Only one significant moderating effect was observed. There was a positive relationship between negative affect at the end of the workday and the number of negative family affective events endorsed by participants who were lower on domain integration, but not among those who were higher on domain integration. The direction of this effect was surprising and may suggest that setting up strong boundaries between life domains creates unattainable expectations, which may increase negative outcomes for an employee. In sum, family-related affective experiences are an important variable to consider when investigating the effects of affective spillover on work-related experiences and health and wellbeing. The failure to do so may result in a considerable loss of information and contribute to mixed study results.