The relationships between maternal age (at birth) and educational and psychosocial outcomes at age 18 were examined in a birth cohort of 1025 New Zealand children. This analysis indicated the presence of consistent tendencies for increasing maternal age to be associated with declining risks of educational underachievement, juvenile crime, substance misuse, and mental health problems. Children with teenage mothers had risks of later adverse outcomes that were 1.5 to 8.9 times higher than the risks for offspring of mothers aged over 30. Subsequent analyses revealed that the associations between maternal age and later educational and psychosocial outcomes were largely, but not wholly, explained by associations between maternal age and the child-rearing practices and home environments experienced by children. In general, increasing maternal age tended to be associated with more nurturant, supportive, and stable home environments. In turn, these linkages between maternal and childhood environment explained most of the association between maternal age and later outcomes. The theoretical and applied implications of these results are considered.