This article examines the relationship between anxiety level and cognitive and emotional development in older preschool children. The study involved 207 children aged 5-6 years (Me = 5.6 years) attending a senior group in a Moscow kindergarten (108 boys and 99 girls). As a result of the cluster analysis, three groups of children were identified: with the low (20.3%), medium (61.8%) and high (17.9%) anxiety levels. We paid special attention to the analysis of the performance on the methods diagnosing executive functions (switching, inhibition and working memory) by children with different anxiety levels. The data obtained testify to the negative effect high anxiety has on the performance of tasks dealing with cognitive flexibility and inhibitory control whereas no connection was established between anxiety and working memory (both auditory and visual). Besides, the data we have obtained indicate a nonlinear connection between the anxiety level, theory of mind development and the understanding of emotions in the preschool age. Thus, this research have shown that the preschooler's anxiety level is a significant internal factor associated with the development of both executive functions and emotional intelligence. In this regard, it is possible to assume that working with anxiety can help harmonize the development of the child and prepare for school.