Aims Alcohol mixed with energy drink (AmED) use is associated with negative consequences including hazardous alcohol use and driving under the influence. While many studies have focused on correlates of AmED use among college samples, very few have examined patterns of AmED use during adolescence and young adulthood within the general population. Accordingly, the purpose of this study is to assess age differences in AmED use among a national sample of respondents aged 18 to 30. Methods The data for this study come from the Monitoring the Future panel study from 2012 to 2015. The sample consists of 2222 respondents between the ages of 18 and 30. Multiple logistic regression using generalized estimating equations (GEE) was used to model past-year AmED prevalence across age and other covariates. Results Nearly half (45.0%) of respondents indicated past-year AmED use at some point during the study period. The lowest prevalence rates were found at age 18 (25.9%) and the highest prevalence rates at age 21/22 (43.5%). GEE analyses indicated a statistically significant positive linear and negative quadratic trend with respect to the association between age of respondent and past-year AmED use. Namely, peak use occurred in early young adulthood (age 21/22 and 23/24) and then declined, reaching 32.0% by age 29/30. College attendance and several substance use behaviors at age 18 moderated these linear and quadratic age trends. Conclusions AmED use peaked rapidly in early young adulthood and declined into later young adulthood. Substance use during adolescence was associated with a higher incidence of AmED use across all young adult ages and a slower decline of AmED use after age 21/22. Several sociodemographic factors were associated with AmED use, particularly college attendance at the age of 21/22.