Objective: Early childhood is considered a window of opportunity for lifestyle interventions, as this is a critical life-stage at which children accumulate knowledge and skills around behaviours such as eating and physical activity. This study examined how exposure to a settings-based healthy lifestyle programme influences knowledge and preference of food and physical play in preschool children. Design: Quasi-experimental, pre-post intervention design. Methods: Pre- and post-impact evaluation of a healthy lifestyle intervention using an innovative computerised photo-pair food and exercise questionnaire and an age-appropriate test of executive function. The study included 82 children aged 3-5 years and was structured with an intervention and a control group. Quantitative data were analysed using SPSS v22. Results: For the intervention group, there was a significant improvement in overall knowledge of healthy lifestyle behaviours post-intervention, particularly in the identification of healthy and unhealthy food choices. There was no associated change in behavioural preferences. Conclusion: The study highlighted that age-appropriate lifestyle interventions with preschool-aged children can lead to improved knowledge of healthy lifestyle choices. However, improvement in knowledge of healthy lifestyle behaviours does not necessarily lead to positive changes in food and activity preferences that inform choices.