This study builds an empirical research model that explores societal and individual antecedents of adult learning and examines the adult learning effect on problem-solving skills in the Organization for Economic Cooperation and Development (OECD) countries. Considering national differences, it uses multilevel data sources available from the Programme for the International Assessment of Adult Competencies (PIAAC) 2008-2013 and the OECD data lab. The results from this study suggest that young adults (25- to 34-year-olds) with more favorable backgrounds benefit from their social origin and occupational environment in terms of nonformal learning participation. It was also found that the participants outperform nonparticipants in the PIAAC problem-solving skill assessment. The key findings of this study advocate for the importance of policy interventions to combat the cumulative effects of multiple disadvantages in the educational trajectory from initial education to adult learning as well as to reduce the problem-solving skill gaps of young disadvantaged adults.