Existing literature on the relationship between interpersonal gratitude and life satisfaction in adolescents has been limited in terms of scope and methodology. Based on the psycho-social model proposed by Alkozei et al. (J Happiness Stud 19:1-24, 2018) and the attachment security enhancement model, this study used a three-wave longitudinal design to test both the mediating role of parent-child relationship and the moderating effect of attachment insecurity in the link between interpersonal gratitude (e.g., gratitude to parents) and life satisfaction among adolescents. A total of 1131 Chinese adolescents (Mage = 12.92, SD = 0.70; 51.5% girls) participated in this study. Overall, the results of the moderated mediation model indicated that, after controlling for baseline life satisfaction, parent-child relationship, age, and sex, interpersonal gratitude was longitudinally associated with parent-child relationship only for adolescents high in attachment insecurity, which in turn predicted improved life satisfaction. These findings have implications for interventions aimed at promoting well-being among adolescents with varying degrees of attachment insecurity.