Background: Population age structure may confound the comparison of age at cancer diagnosis across racial/ethnic groups. We compared age at cancer diagnosis for U.S. Hispanics, a population that is younger on average, and non-Hispanic whites (NHW), before and after adjustment for the age structure of the source population. Methods: We used Surveillance, Epidemiology, and End Results data from 18 U.S. regions in 2015 for 34 cancer sites to calculate crude and adjusted (using age- and sex-specific weights) mean ages at diagnosis. Differences in age at diagnosis comparing Hispanics to NHWs (d) were assessed using independent sample t tests. Results: Crude mean ages at diagnosis were lower among Hispanic males and females for all sites combined and for most cancer sites. After age-adjustment, Hispanic (vs. NHW) males remained younger on average at diagnosis of chronic myeloid leukemia [delta = -6.1; 95% confidence interval (CI), -8.1 to -4.1 years], testicular cancer (delta = -4.7; 95% CI, -5.4 to -4.0), Kaposi sarcoma (d = -3.6; 95% CI,-6.3 to -0.8), mesothelioma (delta = -3.0; 95% CI,-4.3 to -1.7), and anal cancer (delta = -2.4; 95% CI, -3.9 to -0.8), and older at diagnosis of gallbladder cancer (delta = +3.8; 95% CI, 1.8 to 5.7) and Hodgkin's lymphoma (delta = +7.5; 95% CI, 5.7 to 9.4), and Hispanic (vs. NHW) females remained younger at diagnosis of mesothelioma (delta = -3.7; 95% CI, -6.7 to -0.7) and gallbladder cancer (delta = -3.0; 95% CI, -4.3 to -1.7) and older at diagnosis of skin cancer (delta = +3.8; 95% CI, 3.1 to 4.5), cervical cancer (delta = +4.1; 95% CI, 3.3 to 4.8), and Hodgkin's lymphoma (delta = +7.0; 95% CI, 5.0 to 9.1). Conclusions: Onaverage, Hispanics are diagnosed with cancer at younger ages than NHWs; however, for many cancers these differences reflect the younger age structure in Hispanics. Impact: Population age structure should be considered when comparing age at cancer diagnosis across racial/ethnic groups.