This study investigated the impact of family financial socialisation on the financial perceptions and behaviours of adolescents. Drawing from social learning theory, Gudmunson and Danes’ model of family financial socialisation, and the theory of planned behaviour, we examined the influence of family affluence and family financial openness on adolescents’ financial confidence, intentions, and behaviours. The research also explores gender differences and the distinct effects of family socialisation in banking and budgeting contexts. With a large sample of adolescents in New Zealand (n = 5,370), results using structural equation modelling reveal that family affluence corresponds with a higher perception of family financial openness, which influences their confidence in specific financial domains such as banking and budgeting. Our results also highlight a gap between confidence, intentions, and action in financial behaviours, with gender differences also impacting this dynamic. The findings offer insights for parents, policymakers, and financial institutions, emphasising the importance of family financial socialisation in fostering responsible financial practices among young people.