<p>Parental psychological distress can have lasting consequences for children’s development, yet little is known about whether parental distress in infancy predicts children’s distress in late adolescence and, if so, what mechanisms underlie this association. This study investigates the long-term impact of maternal and paternal distress measured in infancy on adolescent distress by considering parent-child relationships in early childhood as potential mediating pathways. Data were drawn from the 17-year longitudinal Millennium Cohort Study in the United Kingdom (<i>N</i> = 16,039 families). Structural equation modelling shows that both maternal and paternal distress measured at 9 months had small but statistically significant effects on adolescent distress at age 17 directly and indirectly via reduced mother-child relationship quality at age 3. However, father-child relationship at age 3 did not mediate the associations between maternal/parental and adolescent distress. Furthermore, a cross-parental effect was observed in explaining adolescent distress that a bidirectional relation existed between maternal and paternal distress, and distress of one parent at 9 months could influence the other parent’s relationship with the child at age 3. Practical implications were discussed.</p>