Democracies rely upon politically knowledgeable citizens for their legitimacy and to sustain themselves. In Australia, policy initiatives have addressed concerns about the low levels of political knowledge among young people. Yet research about how young Australians acquire political knowledge, beyond schools, is scarce. The present study referring to the concepts of situated learning, self-determination and knowledge gap, asks whether young adult's participatory practices (e.g., participation in politics, prior involvement in decision-making at school) predict political knowledge. Analyses that control for multiple predictors of political knowledge suggest differential associations between political knowledge and different participatory practices. Motivational inequality, as defined by interest in politics, moderates the associations with party-political participation and participation at school; the conditional effect of party-related political participation is further moderated by educational resources. Gendered differences are identified for some participatory practices. Directions for future research and the importance of participatory experiences and how to establish a foundation of young citizens' political knowledge are discussed.