Introduction and objective Obesity and chronic diseases represent a major health burden in the Caribbean, particularly since a large part of the population is disadvantaged. However, socioeconomic inequalities in chronic diseases are poorly explored in the Caribbean and the contribution of diet to explain these inequalities has not been studied yet. We therefore investigated the association between socioeconomic position and the prevalence of the metabolic syndrome (MetS) and the mediating effect of diet quality. Methods This cross-sectional analysis included 1144 Guadeloupean and Martinican adults from the Kannari study. Dietary intakes were estimated from 24h dietary recalls and the diet quality was assessed using the Diet Quality Index-International (DQI-I). MetS was defined according to the 2009 harmonized definition, from biological data. Associations between socioeconomic indicators (education, employment status, social assistance benefits, single-parent household, presence of child in the household) and prevalence of MetS, and the mediating effect of diet quality were assessed using multivariate logistic regression models, adjusted for area of residence (Guadeloupe or Martinique), age, sex and body mass index. Results Among Guadeloupean and Martinican adults, MetS prevalence was 23%. Low and middle educated subjects (ORlow vs. high=1.9; 95%CI=[1.0-3.6] and ORmiddle vs. high=2.7; 95%CI=[1.4-5.1]) and recipients of social assistance benefits (OR=2.2; CI95%=[1.1-4.2]) were more likely to be at risk of MetS compared with individuals with high education level and non-recipients. DQI-I explained 11% of the overall educational variation in MetS and only 2% of the overall variation due to social assistance benefits. Conclusions Diet quality slightly contributes to explain the socioeconomic inequalities in MetS in these Caribbean populations. Mediating effect of other lifestyle factors such as smoking status and physical activity are needed to be investigated to better understand mechanisms of socioeconomic inequalities in MetS and therefore to guide future public health measures.