To assess the short-term impact of a nutritional intervention aimed at reducing childhood overweight in German pre-school children. Using a cluster-randomized study design with waiting-list controls, we tested a 6-month intervention administered once weekly by a nutrition expert consisting of joint meal preparation and activities for children and parents such as tasting and preparing nutritious, fresh foods. At baseline, 6 and 12 months, a parent-completed questionnaire assessed fruit and vegetable intakes (primary outcomes) and water and sugared drinks consumption (secondary outcomes). Direct measurement assessed BMI, skinfold thickness and waist-to-height-ratio. An intention-to-treat analysis used random-effects panel regression models to assess the intervention effect, adjusted for each child's age, gender, immigrant background and maternal education. Eighteen pre-schools from three south German regions. Healthy children aged 3-6 years. Three hundred and seventy-seven (80 %) eligible pre-school children participated in the study. Of these, 348 provided sufficient data for analysis. The sample mean age was 4·26 (sd 0·78) years; the majority (53·2 %) were boys. Children's fruit and vegetable intakes increased significantly (P < 0·001 and P < 0·05, respectively); no significant changes in the consumption of water, sugared drinks or anthropometric measurements were noted. Nutritional interventions in pre-schools have the potential to change eating behaviours in young children, which in the long term might reduce risk for developing overweight.