Hispanic adolescents have high expectations for their own educational attainment, but educational attainment outcomes for Hispanic young adults are relatively low on average. Limited scholarship links Hispanic adolescents' educational expectations with attainment in adulthood. Using a longitudinal within-group approach, the authors examined changes in Hispanic adolescents' educational expectations from 10th to 12th grade as well as the discrepancy between educational expectations and later attainment in 2 cohorts (N = 1,372 and N = 1,521). Based on national surveys approximately 12 years apart (NELS:88 and ELS:02), expectations of a college degree became more common for Hispanic adolescents. Most Hispanic young adults attained less education than they expected, and this expectations-attainment gap grew over time, consistent with U.S. national trends. Parent education was positively associated with attaining expectations, and family income became more important for attaining expectations over time. Consistent with the immigrant paradox and immigrant optimism hypothesis, second-generation youth came closer to attaining their expectations than third- or higher-generation youth of equal positioning. Educational expectations and attainment patterns also varied by cohort: for instance, immigrants in the more recent cohort had an absolute disadvantage in terms of attaining their expectations compared with their other-generation counterparts. Finally, parental involvement in education (e.g., parents' educational aspirations) was associated with educational expectations and attainment outcomes. This study advances knowledge of factors that contribute to maintaining and attaining educational expectations for Hispanic youth and how these factors have changed over time. Study results inform efforts to support Hispanic adolescents' and young adults' educational potential. [Support was also provided by the Population Research Institute at the Pennsylvania State University funded by the National Institutes of Health (NIH) infrastructure grant.]