Internalizing disorders are mainly defined as psychosomatic, anxiety and depression problems. The aim of this study was to analyze the relationships between dairy affective states and internalizing disorders in early adolescence (10–12 years old), considering the influence of sex. The participants of the study were 367 children aged between 10 and 12 (190 girls and 177 boys). The results showed that fear was the best predictor for all internalizing disorders, and the only common predictor for all of them. The prediction of boys' internalizing disorders was based only in fear, whereas the prediction for girls involved more variables besides fear. An early detection/regulation of these affective states (particularly fear) may be useful for the prevention and treatment of child internalizing disorders.