PURPOSE: Despite recommended routine vaccination with meningococcal conjugate vaccine (MenACWY) at ages 11–12 years with a booster at age 16 years, national estimates indicate MenACWY uptake is lower in older adolescents than younger adolescents. This study aimed to identify factors associated with MenACWY uptake among adolescents. METHODS: Commercial Claims and Encounters (CCAE) and Medicaid MarketScan Databases from 2011 to 2016 were retrospectively analyzed (2017) to determine receipt of ≥1 dose of MenACWY during early (10.5 through 13 years) and late (15.5 through 18 years) adolescence. Multivariable logistic regression and nonlinear decomposition analyses were used to identify factors associated with MenACWY vaccination, potential missed opportunities, and differences between age groups. RESULT: A larger proportion of younger adolescents than older adolescents received MenACWY: CCAE, 71.7% versus 48.9% (p < .001); Medicaid, 59.3% versus 31.8% (p < .001), respectively. In multivariable models (CCAE), older adolescents were less likely than younger ones to receive MenACWY (adjusted odds ratios [95% confidence intervals]: .68 [.67, .69]) and more likely to have a potential missed opportunity (1.27 [1.25, 1.28]). Decomposition results showed lower MenACWY uptake in older adolescents is largely attributed to fewer non-MenACWY vaccines received, fewer preventive care visits, and interaction with nonpediatric healthcare providers. DISCUSSION: Missed opportunities and infrequent preventive care encounters contribute to lack of vaccination in younger and older adolescents. However, the disparity in uptake between the two age groups was largely attributable to differences in healthcare utilization, suggesting a need for unique strategies to increase uptake among older adolescents, such as solidifying a vaccination platform for ages 16–18 years through encouragement of annual preventive care visits.