Abstract Objective To assess the effect of the Dutch school-based education programme ‘Taste Lessons’ on children’s behavioural determinants towards tasting unfamiliar foods and eating healthy and a variety of foods. Design In a quasi-experimental study design, data on behavioural determinants were collected at baseline, four weeks and six months after the intervention in both the intervention and control group. Children completed consecutively three questionnaires in which knowledge, awareness, skills, attitude, emotion, subjective norm and intention towards the two target behaviours were assessed. Teachers implemented on average a third of the programme activities. Multilevel regression analyses were conducted to compare individual changes in the determinants in the intervention group with those in the control group, corrected for children’s gender and age. Effect sizes were expressed as Cohen’s d . Setting Dutch elementary schools. Subjects Forty-nine classes (1183 children, 9–12 years old) in grades 5–8 of twenty-one elementary schools. Results The intervention group showed a higher increase in knowledge ( d =0·26, P <0·01), which persisted after six months ( d =0·23, P <0·05). After four weeks, the intervention group showed a higher increase in number of foods known ( d =0·22, P <0·05) and tasted ( d =0·21, P <0·05), subjective norm of the teacher ( d =0·17, P <0·05) and intention ( d =0·16, P <0·05) towards the target behaviours. Conclusions Partial implementation of Taste Lessons during one school year showed small short-term effects on increasing behavioural determinants in relation to tasting unfamiliar foods and eating healthy and a variety of foods. Full and repeated implementation of Taste Lessons in subsequent years might result in larger effects.