The aim of this cross-sectional study was to investigate potential associations of child temperament with child weight and breakfast habits. It was hypothesised that children with externalising temperament were more likely to be overweight/obese, and that externalising temperament was associated with not eating daily breakfast. Temperament was controlled for by various child and parental covariates. The sample consisted of 18,047 five-year-olds from the Norwegian Mother and Child Cohort Study (MoBa). Temperament scales were created through principal component analysis (PCA) that showed three dimensions; internalising, externalising, and sociability. Child weight was measured with body mass index percentile-scores, and breakfast habits were differentiated between daily and not daily breakfast. One-way analysis of variance (ANOVA) and Pearson chi-square test of independence were used to assess category differences in the independent variables in relation to the dependent variables. Binary logistic regression was employed to predict categorical outcomes; weight and breakfast. When controlling for other variables, the results showed that children who scored higher on the externalising scale were at a greater risk of being overweight/obese. Those who scored higher on the internalising scale had lower odds of being overweight/obese. Externalising temperament was associated with breakfast consumption, with higher scores indicating lower probability of the child eating daily breakfast. The temperament dimension termed sociability was not significantly associated with weight or breakfast. This thesis study has shown for the first time an association between temperament and weight based on the MoBa sample. Additionally, an association between temperament and breakfast consumption is a novel finding. Access to already retrieved data was provided by the Norwegian Institute of Public Health. This thesis study was independent, not related to a research project.