Self-regulation is an important core skill of the 21st century. However, scientific approach together with suggestions for improving self-regulation at school has remained on the background [1]. Self-regulation is affected by several external and internal factors, but the latter ones are described mainly in a few theoretical models and hardly found in empirical studies. The aim of the current research was to better understand the role of one of the internal factors - self-concept clarity - in predicting self-regulation. The Estonian Self-Concept Clarity Scale [2] and an adapted version of the Adolescent Self-Regulatory Inventory [3] were used as part of an online survey. Altogether 648 high school students participated. Results of linear regression showed that 22% of self-regulation variability is explained through self-concept clarity. The study provides initial evidence on the importance of internal factors for gaining a better understanding of adolescent self-regulation. Understanding different predictors is important to better support the development of self-regulation in school context.