Body mass index (BMI) is an important health indicator that changes with age and may be shaped in important ways by prior military service. While a high proportion of older men in the United States served in the military, to date, there has been no longitudinal, population-representative study of veteran status differences in men’s mid- to late-life BMI trajectories. In this chapter, we use data from the 1992–2010 Health and Retirement Study (HRS) and growth curve models to examine veteran status differences in mid- to late-life BMI trajectories for cohorts of men born in the United States during the first half of the twentieth century. Without any controls in the models, veterans exhibit lower BMI, on average, than non-veterans. Once we add controls for birth cohort, early-life characteristics that occur prior to military service, potentially mediating mid- to late-life characteristics, and methodological controls for proxy report, attrition, and death during the study period, the effect of veteran status is small, marginally significant, and positive—net of other factors, veterans are marginally heavier than their non-veteran counterparts. Taken together, our analyses demonstrate the large effect of the secular trend in increased weight across the population—younger cohorts are substantially heavier than older cohorts regardless of their veteran status—and a substantively small but consistent, positive intra-cohort effect of veteran status.