We tested birth order effects on selection into different careers (scientific, artistic, and creative) and status attainment (educational attainment, occupational prestige, and income) using a large sample ( n = 3763), a longitudinal design, and relevant controls. Additionally, we tested mediation of birth order effects on career outcomes via personality traits, intelligence, and educational attainment. We found negligible birth order effects ranging from 0.02 to 0.12 on a correlational metric, where firstborns (vs. laterborns) selected into more creative careers and attained higher prestige and education. Conditional on the theoretically based mediation models tested, results showed that intelligence and educational attainment (but not personality traits) accounted for a statistically significant portion of the variance in the links between birth order and career outcomes. No direct effects of birth order on career outcomes remained when accounting for indirect effects through educational attainment. These findings bring modest support to the confluence model, no support to the niche-finding model, and suggest that one possible route via which birth order might impact career outcomes (if at all) could be via educational attainment.