Mounting research supports that co-rumination, the tendency to seek peer support by engaging in extensive negatively focused discussion, is a risk factor for adolescent psychopathology. It is unclear, though, how this interpersonal tendency develops. Parental responses to adolescents' negative affect likely shape how youth utilize peer relationships to regulate distress, as they shift to reliance on peer support during this developmental stage. For example, nonsupportive parental responses may fail to instill healthy regulation strategies, resulting in ineffective forms of peer support, such as co-rumination. Conversely, high levels of supportive parental responses to adolescents' negative affect may motivate youth to also express more negative affect with peers, leading to co-rumination. Eighty-nine healthy adolescents (9-17) and their mothers completed surveys and a support-seeking interaction. Only supportive maternal responses, including maternal affection, were associated with adolescents' co-rumination. These analyses indicate that some forms of parental support are associated with adolescents' tendency to co-ruminate.