In recent decades, the average age of the United States workforce has been on the rise, a trend that is expected to continue as the Baby Boomer generation, which constitutes the largest segment in the workforce in this country, reaches older adulthood. The aging of the workforce has raised concerns from researchers, policy-makers, and organizations. As a result, there have been calls for research regarding how experiences at work vary across the life-span, although few studies have addressed this topic. To begin to address this gap in the literature, this dissertation aims to explore the association between job demands and well-being and how the processes employees use to cope with job demands vary with age. Using data from two waves of Midlife in the United States: A National Study of Health and Well-Being, with a sample of over 7,000 working adults ranging from ages 20 to 83, I attempt to integrate the Job Demands-Control-Support Model with the Life-Span Theory of Control in order to examine how multiple factors influence the relationship between job demands and well-being outcomes across the life-span. Results of random effects linear regression models show that job demands were negatively related to job satisfaction and mental health and that the relationship between job demands and job satisfaction was weakest at younger ages and remained constant after midlife. With regard to the factors that moderate the relationships with job demands, findings indicated that job control and job support buffered the relationship with job satisfaction, while job support buffered the relationship with mental health. The buffering roles of job control and job support were found to vary based on levels of primary and secondary control for workers of different ages. Findings are discussed in terms of their implications for both workplace theory and developmental theories, which help to provide a better understanding of how work experiences vary across the life-span.