As decriminalization, increased access, and decreased perception of risk spurs the popularity of medical and recreational marijuana, more information is needed on possible links between marijuana use and social determinants of health. The goal of this study was to assess the relationships between marijuana use and exercise. Data sources included the two most recent waves of the National Longitudinal Study of Adolescent to Adult Health (Wave IV, 2008–2009; N = 14,784 and Wave V, 2016–2018; N = 12,043). The exercise variables included any form of exercise/sport during the past 7 days and the number of days participating in each of 7 types of exercise/sport. Marijuana-use variables comprised any current use and frequency of use during the past 30 days. Both fixed-effects and random-effects models were estimated with numerous control variables, along with binary and count measures of exercise. Results show that, particularly for fixed-effects models, marijuana use is not significantly related to exercise, counter to conventional wisdom that marijuana users are less likely to be active. Indeed, the only significant estimates suggest a positive relationship, even among heavier users during the past 30 days. These findings are at odds with much of the existing literature, which generally shows a negative relationship between marijuana use and exercise. As additional states legalize the medicinal and recreational use of marijuana, perhaps its impact on exercise, one of the leading social determinants of health, is not necessarily a primary concern.