African American youth use marijuana at similar rates and tobacco at lower rates compared with white youth; however, in adulthood, tobacco use is similar. Tobacco and marijuana use are closely associated; differing initiation patterns may contribute to observed racial differences in tobacco prevalence by age. Therefore, it is important to assess tobacco and marijuana initiation patterns by race. Data were obtained from 56 555 adults aged 18-25 who completed the 2005-2012 National Survey on Drug Use and Health. The analysis was restricted to those who reported ever use of marijuana and combustible tobacco (cigarettes and/or cigars). Three mutually exclusive categories of initiation patterns were evaluated: use of marijuana before tobacco; marijuana and tobacco at the same age; and tobacco before marijuana. Multivariable regression models were used to assess changes over time and compare these outcomes by race while controlling for sociodemographics, risk perceptions, and current substance use. In 2005, 26.6% of African American and 14.3% of white young adults used marijuana before tobacco, compared with 41.5% of African American and 24.0% of white young adults in 2012 (P < .001). Overall, African American young adults had greater odds of using marijuana before tobacco (AOR = 1.79; 95% CI: 1.67, 1.91) compared with whites. African American young adults were more likely than whites to use marijuana before tobacco and both groups were increasingly likely to use marijuana before tobacco over time. A greater understanding of how marijuana initiation interacts with tobacco initiation could inform more effective tobacco and marijuana use prevention efforts. Among ever users of combustible tobacco and marijuana, greater proportions of African American young adults used marijuana before tobacco or at the same age than their white counterparts. Moreover, both African Americans and whites were more likely to use marijuana before tobacco in 2012 compared with 2005. Tobacco control policy may benefit from a broader understanding of the patterns of initiation to tobacco and marijuana use. Some public health interventions aimed at preventing and reducing combustible tobacco use among African American young adults may be strengthened by considering marijuana use.