The job demands-resources (JD-R) model suggests that work environment can be categorized into job demands and job resources, and that each has a significant impact on job attitudes, particularly on job stress and burnout. High job demands and low job resources create physical and psychological strain, which leads to negative job-related mental health. Socioemotional selectivity theory (SST) and lifespan development and work motivation theory further suggest that people experience changes in cognitive ability, values, life goals, and affect with age. I propose that these age-related changes lead to changes in perceptions of work environment over time. The purpose of this research is to investigate how perceptions of work environments (e.g., job demands, job resources) change over a 19-year period and factors that influence and result from these changes. The study explored how changes in perceived work environments were influenced by changes in job characteristics (supervisor status, job complexity), and how the changes in perceived work environments influenced changes in job-related mental health over time. The current study uses participants (N = 1,036) from three waves of data over a 19-year study period from Midlife in the United States: A National Study of Health & Well-Being (MIDUS), which uses a national sample of Americans. The study used latent growth curve modeling to find that perceptions of job demands (b = -.132) and coworker support (b = -.053) decreased over time. The decline in job demands was greater in the older group (b = -.259, p < .001), but the decline in coworker support was greater in the younger group (b = .091, p < .05). Changes in supervisor status influenced the changes in perceived work environment (b = .335 to .383), but changes in job complexity did not influence the changes in perceived work environment. There was a positive relationship between changes in job-resources and job-related mental health (b = .524 to .1045), but the relationship between changes in job demands and job-related mental health was not significant. The study has the potential to help organizations create work environments that improve the productivity and well-being of employees across their working lifespan.