Social change and the aging process are racially bifurcated in the United States, where Black and White populations have long lived in divergent social worlds. This study examines the cohort patterns and life-course trajectories of Black and White homicide involvement over the past four decades. The study uses data from the Supplemental Homicide Reports and Age-Period-Cohort-Interaction (APC-I) models to analyze race-specific trends of (alleged) homicide offending and victimization between 1976 and 2018 in the U.S. Results reveal similar patterns in the age, period, and cohort effects on Black and White homicide involvement. However, while the shapes of these trajectories are comparable, the volatility in cohort effects on homicide is much more accentuated for Black cohorts than White cohorts. We also find racial differences for cohorts born after 1990, with a downward cohort pattern among the White group but a flat cohort trend among the Black group. Findings suggest that Black cohorts' homicide involvement is more susceptible than White cohorts' to the influence of external social changes (e.g., economic downturn, the crack epidemic). In addition, an increasing racial gap between Black and White populations is found among the recent birth cohorts. Possible mechanisms are discussed.