The goal of this study was to examine, in a nationally representative sample, relationships between various sexual initiation patterns, subsequent sexual partnerships, and related health outcomes from adolescence through early adulthood. Data were from a subset of 6587 respondents from the National Longitudinal Study of Adolescent to Adult Health. Bivariate analyses and adjusted logistic and ordinary least squares regression models were used to determine associations between membership in three sexual initiation classes, lifetime sexual partner counts, and multiple health outcomes, including lifetime sexually transmitted infection or disease (STI/STD) diagnosis, lifetime unintended pregnancy, and romantic relationship quality. Broadly, having fewer lifetime sexual partners was associated with lower odds of STI/STD diagnosis and unintended pregnancy, and better relationship quality; however, findings also indicated both within and between sexual initiation class differences in the relationship between lifetime sexual partners and all three health outcomes. In particular, results showed little variation in health outcomes by sexual partnering among those who postponed sexual activity, but members of the class characterized by early and atypical sexual initiation patterns who had fewer lifetime partners exhibited better health outcomes than most other initiation groups. These results show that while both sexual initiation and partnering patterns add important information for understanding sexual health from adolescence to early adulthood, partnering may be more relevant to these sexual health outcomes. Findings indicate a need for more comprehensive sexuality education focused on sexual risk reduction and promotion of relationship skills among adolescents and adults.