Objective: To study diet quality among pre-schoolers using the Diet Quality Index (DQI) and to investigate differences according to gender, socio-economic status (SES) and overweight/obesity status. Design: Kindergarten-based cross-sectional survey within the ToyBox-study. A standardized protocol was used and parents/caregivers self-reported sociodemographic data and a semi-quantitative FFQ. A total DQI and its four subcomponents (diversity, quality, equilibrium and meal index) were calculated based on this FFQ. High total DQI scores indicate better diet quality than low scores. Results of the total DQI and the subcomponents were reported as percentages of maximum scores (100 %). Setting: Kindergartens in six European countries (Belgium, Bulgaria, Germany, Greece, Poland and Spain). Subjects: European pre-schoolers (aged 3·5-5·5 years) and their parents/caregivers (n 7063). Results: The mean total DQI score was 68·3 %. Mean scores of the subcomponents were 61·7 % for diversity, 56·5 % for quality, 65·4 % for equilibrium and 89·7 % for the meal index. Pre-schoolers of lower-SES backgrounds had lower scores on the total DQI and all its subcomponents. No clear differences were found by gender and overweight status. Results differed slightly according to country. Conclusions: Pre-schoolers scored low on the total DQI and especially on dietary quality, as energy-dense, low-nutritious food items were more often consumed than highly nutritious food items. Furthermore, already in pre-schoolers lower-SES mothers were less likely to provide a good diet quality and this was consistent for all four subcomponents of the total DQI. Food intake in pre-schoolers should be enhanced, especially in pre-schoolers of lower-SES backgrounds.