The Guidelines for the implementation of Article 11 of the World Health Organization (WHO) Framework Convention on Tobacco Control (FCTC) require that cigarette health warning labels should include pictures and take up 50% or more of the principal display area. This study examined how the association between large pictorial warnings, those covering ≥50% of the front and back of the package, and the prevalence of cigarette smoking varies by educational attainment. We pooled individual-level tobacco use data from the Global Adult Tobacco Survey (GATS) in 18 countries between 2008 and 2013 and linked them with warning label requirements during the same period from the MPOWER database and reports regarding warnings. The respondents' self-reported exposure to warnings was examined according to education. Logistic regressions were further employed to analyze education-specific associations between large pictorial warnings and smoking prevalence, and whether such association differed by education was examined using an interaction test. At the time of the survey, eight out of 18 countries had imposed graphic warning labels that covered ≥50% of the package. These warnings were associated with a 10.0% (OR = 0.89; 95% CI: 0.81, 0.97; p ≤ 0.01) lower cigarette smoking prevalence among adults with less than a secondary education or no formal education, but not among respondents with at least a secondary education. Less educated respondents were also less likely to be exposed to warnings in all 18 countries. The association between strong warnings and lower smoking prevalence among less educated respondents could be greater if their exposure to warnings increases. Prominent pictorial warning labels can potentially reduce health disparities resulting from smoking across different education levels.