Literature shows that parental financial socialisation plays an important role in attaining financial literacy as well as in shaping sustainable financial behaviours and that both translate into increased well-being indicators and financial security on micro- and macroeconomic levels. However, debt literacy and debt behaviour seem to be unique. Very little is known about the childhood financial socialisation process through which adults’ sustainable debt behaviour is shaped and how debt behaviour may affect well-being. This study tests a hierarchical model of childhood financial socialisation consisting of five levels: the anticipatory parental socialisation, and later life financial learning outcomes (particularly, debt literacy levels), financial attitudes, debt behaviour, and well-being. Using data collected from a purposive sample of young adult Poles (N = 600) during the period from 10 to 13 November 2018 and employing structural equation modelling, we have found evidence confirming the hierarchical relationship of literacy–attitude–behaviour. Our data do not support, however, either the hypothesised positive relationship between parental socialisation and objectively measured debt literacy or the assumed relationships between debt behaviour and well-being indicators. We posit that country-specific factors related to generational differences entailed by system-wide transition and the specificity of debt behaviour, respectively, are key for explaining these empirical deviations from the assumed conceptual framework. Finally, we found no significant differences between the models estimated separately for maternally conditioned and paternally conditioned respondents.