Both juvenile and adult nutritional environment (e.g. macronutrient composition) can alter developmental trajectories, independently or interactively, to shape behaviour in later life. Moreover, variation in macronutrient composition across life stages can lead to among-individual covariation between behaviours (‘behavioural syndromes’) as well as among-individual variation in single behaviours (‘personality’). In this study, we used field crickets Gryllus bimaculatus and a split-brood experimental design to compare the expression of behaviours, their among- and within-individual variances across nutritional conditions. We showed that effect of macronutrient compositions on the mean level of behaviour was generally associated with the change in variance components in the behaviour. However, sometimes variance components in behaviours changed independently from the diet effect on mean level. Interestingly, we also found that diet effect on behavioural syndromes could be independent from diet effect on the mean level of behaviour and its variance components. As a consequence, we suggest that nutritional condition can assert a direct influence on the covariation between behaviours. This implies that expressions of genes with pleiotropic effects differ in their directions between nutritional environments.