This four-year, multi-informant longitudinal study (N=480, initial age: 15) investigated the interplay between parental support, behavioral-and psychological control, and adolescents' emotion regulation development. We examined reciprocal effects between parents and children, mothers' versus fathers' unique roles in emotion regulation development, and sex differences.Multi-informant data allowed us to compare effects of adolescent-perceived and parent-reported parenting. Finally, innovative analyses allowed us to disentangle between-family differences from within-family predictive processes. Parenting and emotion regulation were associated at the between-family and within-family levels, especially according to adolescent reports. Support primarily played a role between mothers and adolescents, and perceived behavioral control between fathers and adolescents. Sex moderation revealed that support played a more prominent role in mother-daughter than mother-son relationships, and that daughters experienced greater behavioral control. Child effects outnumbered parent effects, which might reflect the increasing equality of adolescent-parent relationships. Finally, adolescent-perceived parenting was a stronger correlate of emotion regulation than parent-reports, suggesting that adolescents' perceptions are a relevant source of information for research and practice. Consistent with the self-determination theory perspective on parenting, emotion regulation flourished when adolescents felt like mothers provided support, and fathers loosened behavioral control. These results are in line with the notion that mother-child relationships are supportive attachment relationships, whereas fathers provide "activation" relationships, challenging adolescents to regulate emotions autonomously by providing less explicit structure.