Additional supporting information can be found at http://pss.sagepub.com/content/by/supplemental-data . Data files are available from University of London, Institute of Education, Centre for Longitudinal Studies via the UK Data Service (http://ukdataservice.ac.uk/). Safeguarded data are provided under the UK Data Service’s end user license. ; Each year, 15 million babies are born preterm worldwide. Preterm birth is associated with adverse neurodevelopmental outcomes across the lifespan. Recent registry-based studies suggest that preterm birth is associated with lower wealth in adulthood, but the mediating mechanisms are unknown. This study investigated whether the relationship between preterm birth and low adult wealth is mediated by poor academic abilities and educational qualifications. Participants were members of two British population-based birth cohorts born in 1958 and 1970. Results showed that preterm birth was associated with decreased wealth at 42 years of age. This association was mediated by poorer intelligence, reading and, in particular, mathematics attainment in middle childhood, and lower educational qualifications in young adulthood. Findings were similar in both cohorts, suggesting that these mechanisms may be time invariant. Special educational support in childhood may prevent preterm children from becoming less wealthy as adults. ; We are grateful to the Centre for Longitudinal Studies (CLS), Institute of Education, University of London and UK Data Archive for the use of these data. This study was funded by the Nuffield Foundation (Grant number: EDU/40442). ; Peer-reviewed ; Post-print