--- - |2 Abstract Maternal presence has marked effects on adolescent neurocognition during risk taking, influencing teenagers to make safer decisions. However, it is currently unknown whether maternal buffering changes over the course of adolescence itself, and whether its effects are robust to individual differences in family relationship quality. In the current longitudinal study, 23 adolescents completed a risk‐taking task under maternal presence during an fMRI scan before and after the transition to high school. Behavioral results reveal that adolescent risk taking increased under maternal presence across a one‐year period. At the neural level, we found that adolescents reporting higher family conflict showed longitudinal increases in functional coupling between the anterior insula (AI) and ventral striatum (VS) when making safe decisions in the presence of their mother, which was associated with increased real‐world risk taking. These findings show that individual differences in family relationship quality undermine effective development of AI‐VS connectivity resulting in increased risk taking. - Developmental Science, Volume 21, Issue 5, September 2018.