Non-formal adult education (NFE) provides adults of all ages with the opportunity to acquire skills, knowledge, and expertise. However, there is currently a lack of validated instruments that measure the factors of NFE non-participation in European countries, particularly their barriers. One exception is the Non-participation in Non-formal Education Questionnaire (NP-NFE-Q). This study evaluates and compares the psychometric properties of this instrument among adults across four purposefully selected European countries: Sweden, Germany, the United Kingdom, and the Czech Republic. The results indicate a good model fit for a three-factor model across randomly split pooled samples and for all countries (min. CFI, TLI, and GFI = 0.932, 0.908, and 0.941, max. RMSEA = 0.079). The findings reveal that adults currently face barriers in three key forms: (1) worries and (2) needs regarding NFE at the micro level and (3) the need for more suitable provision at the macro level.