The present study investigated a direct assessment of behavioral self-regulation (the Head-Toes-Knees-Shoulders; HTKS) and its contribution to early academic achievement among young children in Germany and Iceland. The authors examined the psychometric properties and construct validity of the HTKS, investigated gender differences in young children's behavioral self-regulation, and explored relations between the HTKS and a teacher report of behavioral self-regulation (the Child Behavior Rating Scale; CBRS) and emerging academic skills. Findings supported the construct validity of the HTKS when used with young German and Icelandic children. Multilevel analyses revealed gender differences, particularly on the CBRS teacher-rated measure. Finally, higher levels of behavioral self-regulation were related to higher academic skills after important background variables were controlled, although some cross-cultural differences in the predictive utility of the HTKS and CBRS were observed. Overall, these results extend prior psychometric work on the HTKS to samples of young European children and support the importance of understanding of the role behavioral self-regulation in young children's development. (Contains 6 tables.)