BACKGROUND: Adolescents and young adults (AYAs) ages 15 to 39 years with cancer continue to experience disparate survival outcomes compared with their younger and older counterparts. This may be caused in part by differential access to specialized cancer centers (SCCs), because treatment at SCCs has been associated with improved overall survival. The authors examined social and clinical factors associated with AYA use of SCCs (defined as Children's Oncology Group-designated or National Cancer Institute-designated centers). METHODS: A retrospective, population-based analysis was performed on all hospital admissions of AYA oncology patients in California during 1991 through 2014 (n = 127,250) using the Office of Statewide Health Planning and Development database. Multivariable logistic regression analyses examined the contribution of social and clinical factors on always receiving care from an SCC (vs sometimes or never). Results are presented as adjusted odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: Over the past 20 years, the percentage of patients always receiving inpatient care at an SCC increased over time (from 27% in 1991 to 43% in 2014). In multivariable regression analyses, AYA patients were less likely to always receive care from an SCC if they had public insurance (OR, 0.64; 95% CI, 0.62-0.66), were uninsured (OR, 0.51; 95% CI, 0.46-0.56), were Hispanic (OR, 0.88; 95% CI, 0.85-0.91), lived > 5 miles from an SCC, or had a diagnosis other than leukemia and central nervous system tumors. CONCLUSIONS: Receiving care at an SCC was influenced by insurance, race/ethnicity, geography, and tumor type. Identifying the barriers associated with decreased SCC use is an important first step toward improving outcomes in AYA oncology patients. Cancer 2017;123:2516–23. © 2017 American Cancer Society.