During the transition to adolescence, several developmental trends converge to increase the importance of peer relationships, the likelihood of peer-related stressors, and the experience of depressive symptoms. Simultaneously, there are significant changes in parent-child relationships. The current study sought to evaluate whether positive relationship quality with parents continued to serve a protective effect by buffering the relationship between stressful life events, especially peer stress, and increases in depressive symptoms throughout the transition to adolescence. Participants in a large (N = 692) 2-site accelerated longitudinal study were recruited in 3rd, 6th, and 9th grade and followed every 3 months for 1 year. At baseline, parents and youth reported on parent-child relationship quality, and every 3 months thereafter reported on their levels of stressors and depressive symptoms. Parent relationship quality moderated the relationship of person-level fluctuations in peer stressors, such that there was a stronger association between peer stressors and increases in depressive symptoms in youth with lower levels of positive parental relationship quality. This effect was specific to peer stressors. These results suggest that low levels of parent relationship quality leave youth particularly vulnerable to the depressogenic effects of peer stressors from childhood through adolescence.