Nonformal adult education (NFE) provides adults with the opportunity to obtain competences needed to adapt to today's changing job market. Despite the well-documented positive effects of NFE, there remains a lack of valid research instruments to assess factors of nonparticipation. Specifically, defining the perspectives of social groups with the highest incidence of barriers and the lowest level of participation in NFE has not been a primary research goal. This study describes the development and initial validation of a novel research tool entitled the Nonparticipation in Nonformal Education Questionnaire (NP-NFE-Q). The analysis covers the use of the NP-NFE-Q on a representative sample of the adult population (n = 878) as well as three additional cohorts: low-educated workers (n = 227), persons caring for children under the age of three (n = 227), and retired persons (n = 232). The results consistently support the validation of a correlated five-factor model, which includes two situational, one institutional and two dispositional factors.