The present study aimed to examine whether a multibehavioural intervention with a focus on specific energy balance-related behaviours can affect total diet quality and its four subcomponents in European preschoolers and to investigate if these intervention effects differed by socioeconomic status (SES). Parents/caregivers of 3.5 to 5.5 year-olds (n = 4968) recruited through kindergartens in six European countries within the ToyBox-study completed questionnaires on socio-demographics and a food frequency questionnaire on their preschoolers' diet. To assess intervention effects and differences by SES, multilevel repeated measures analyses were conducted. In contrast to no significant difference in total diet quality, in both the intervention and control group, the dietary quality and dietary equilibrium increased, with a larger increase in the intervention group (mean difference (quality): + 3.4%;mean difference (equilibrium): +0.9%) compared to the control group ((quality): + 1.5%;(equilibrium): + 0.2%). SES was not a significant moderator for intervention effects on total diet quality, nor for the four subcomponents. This study indicates that multibehavioural interventions with a focus on specific energy balance-related behaviours in preschoolers not only affect those targeted behaviours, but can also have more generalized effects. The ToyBox-intervention effects were similar for both lower and high SES preschoolers.