Structural equation modelling (SEM) with longitudinal survey data was used to test a proposed developmental model of the association of family income (with children aged 6–9) to parent behaviours (for children at 10 years of age) and adolescent cognitive achievement and behaviour problems (at age 15). Data from the Child Development Supplement and Panel Study of Income Dynamics provided a representative US sample (n = 953). The SEM measurement model of parent behaviours showed two robust latent variables representing parent distress (based on two measures) and parent support (composed of four measures of parent investment, cognitive stimulation, emotional warmth, and educational expectations for the child). The SEM structural model indicated that the relation between average family income between 1998 and 2001 for young children (ages 6–9) and adolescent cognitive achievement and behaviour problems in 2007 (age 15) was almost entirely mediated by parent distress, parent support, and material hardship, all measured in 2002. Results suggested that the structural model was strongest (RMSEA = 0.08) when all three mediating variables were included. These results provide a clearer picture of the developmental mechanisms by which family income becomes associated with adolescent cognitive achievement and behaviour problems over time.