The well-documented opposition to trade openness among the less educated is frequently interpreted in terms of the factor endowment model, suggesting that it is the insecure economic position of the less educated that underlies their disapproval. This theory is, however, contested. Consequently, we have developed two alternative explanations, dereification theory and political-knowledge theory, which are informed by the literature on economic globalisation and the broader literature in cultural and political sociology and political science. We test these three theories by analysing Dutch survey data ( N = 1302). We reveal that higher levels of opposition to trade openness among the less educated can, in order of salience, be attributed to: (1) their lower levels of cultural capital (in line with dereification theory), (2) their lower incomes (in line with economic-insecurity theory), and (3) their lower levels of political knowledge. We discuss the broader implications of our findings, including the relevance of cultural capital and dereification theory for understanding various types of cultural conservatism among the less educated, and we provide suggestions for further research into opposition to trade openness among specific segments of higher social strata.