There are currently no instruments available to measure social cognitions towards food choice in children. This study aimed to test the feasibility and predictive validity of a novel measurement tool to assess food-related social cognitions. Sixty-eight children, five to eight years old, were asked to sort cards with photographs of four fruit and four sweet/savoury snacks as a mean to measure attitudes, subjective norms, perceived behavioural control (PBC), and intention. Subsequently, food choice (dependent variable) was assessed using a laboratory food choice task in which children could gain access to sweet and savoury or fruit items, or a combination. All participants completed the tasks successfully, demonstrating feasibility of the procedure. The order in which the cards were sorted for each construct differed sufficiently and correlations between constructs were in line with previous studies. Measures of PBC, intention, attitude, and subjective norm from the mother, but not from teachers or friends, correlated significantly with subsequent food choice. It is possible to measure food-related social cognitions in children aged five to eight and these measures were predictive of observed behaviour. The new instrument can contribute to our understanding of psychological determinants of food choice in young children.