Introduction: In the early years of schooling, factors such as being far from parents for 5 hours, academic and social demands can be stressful for children and provide the conditions for creating or intensify some mental disorders. Therefore, it is important to investigate the prevalence of emotional-behavioral disorders and their related factors at this age. Aim: The purpose of the present study was to investigate the prevalence of emotional-behavioral disorders with and without comorbidity in children aged 6 to 8 years, and also to predict the severity of these disorders based on the mother's reaction to the child's negative emotions. Method: The research method was descriptive-analytical. The population included all the first and second grade primary school students of Malayer city in the academic year 2017-2018, and 454 people were selected by cluster sampling method. In order to collect data, the Child's Behavior Checklist (2002) and the Child's Reaction to Negative Emotions Questionnaire (1990) were used. Data were analyzed through SPSS version 22 software and stepwise linear regression model was employed. Results: The findings of the present study revealed that, the pure prevalence of emotional and behavioral disorders in these children was 8.6% and prevalence with comorbidity of these disorders was 7.3%. In addition, mother's reactions to children's negative emotions could predict the severity of children's emotional-behavioral problems (P=0.001). Conclusion: In the age range of 6 to 8, the comorbidity of emotional and behavioral disorders of these children is high and the mother's supportive or unsupportive reactions to the child's negative emotions play a significant role in it, so it is suggested that child psychologists and psychiatrists pay special attention to these findings in diagnostic interviews and treatment strategies.