Abstract-Johnston & Pennypacker (1993) stated "Behavior" is defined as the action or activities of an organism that is anything that an organism does, including physical action, internal physiological and emotional processes and implicit mental activity. Teaching can in fact, be defined as conscious behavior that makes learning more probable and more efficient than it would have been without that behavior (as cited in Shafgat, 2009). The major purpose of the study was to investigate the relationship between EFL teachers' behaviors and the academic achievement of the high school students in Iran. Sixty two High school English teachers from Sistan and Baluchistan were selected via the purposive sampling procedure. One questionnaire, for EFL high school teachers was developed for the collection of data. The data of the study were collected and analyzed through appropriate statistical techniques such as descriptive statistics and inferential statistics (Pearson correlation and linear regression analysis).The results of the study showed that there is significant relationship between Iranian EFL teachers' behavior and academic achievement of high school students. The results also showed that cognitive and psychomotor behavior of EFL teachers could predict academic achievement of students. Therefore, it could be argued that all dimensions of teachers' behavior could not predict academic achievement of high school students.Index Terms-EFL teachers, behavior, academic achievement, cognitive behavior, affective behavior, psychomotor behavior