Background The aim of the current study was to compare levels of energy balance-related behaviours (physical activity, sedentary behaviour, and dietary behaviours (more specifically water consumption, sugar-sweetened beverage consumption and unhealthy snacking)) in four-to six-year-old preschoolers from six European countries (Belgium, Bulgaria, Germany, Greece, Poland, and Spain) within the ToyBox cross-sectional study. Methods A sample of 4, 045 preschoolers (4.77 +/- 0.43 years; 52.2% boys) had valid physical activity data (steps per day), parents of 8, 117 preschoolers (4.78 +/- 0.46 years; 53.0% boys) completed a parental questionnaire with questions on sedentary behaviours (television viewing, computer use, and quiet play), and parents of 7, 244 preschoolers (4.77 +/- 0.44 years; 52.0% boys) completed a food frequency questionnaire with questions on water consumption, sugar-sweetened beverage consumption and unhealthy snacking. Results The highest levels of physical activity were found in Spain (12, 669 steps/day on weekdays), while the lowest levels were found in Bulgaria and Greece (9, 777 and 9, 656 steps/day on weekdays, respectively). German preschoolers spent the least amount of time in television viewing (43.3 min/day on weekdays), while Greek preschoolers spent the most time in television viewing (88.5 min/day on weekdays). A considerable amount of time was spent in quiet play in all countries, with the highest levels in Poland (104.9 min/day on weekdays),and the lowest levels in Spain (60.4 min/day on weekdays). Belgian, German, and Polish preschoolers had the lowest intakes of water and the highest intakes of sugar-sweetened beverages. The intake of snacks was the highest in Belgian preschoolers (73.1 g/day) and the lowest in Greek preschoolers (53.3 g/day). Conclusions Across six European countries, differences in preschoolers' energy balance-related behaviours were found. Future interventions should target European preschoolers' energy balance-related behaviours simultaneously, but should apply country-specific adaptations.