Existing research finds that succeeding immigrant generations are at greater risk for mental health problems as well as higher levels of substance use. Previous studies have attempted to unpack the role of acculturation stress, discrimination, and other factors in these outcomes. Using data from a community-based sample of Miami-Dade County young adults, we use an empirically and theoretically precise measurement of generational status, allowing us to better understand the process of acculturation and adaptation experienced by each generation. Our results are consistent with theories on the relationship between exposure to social stress and substance use. We find that first-generation immigrants have less exposure to social stress and as a consequence are at a decreased risk for involvement in substance use compared to second- and third-generation immigrants, who report being exposed to higher levels of social stress and higher levels of substance use.