Extensive research has been conducted on teachers' classroom practices, particularly instructional and behavior management practices that are linked to students' learning. However, research on teaching practices in Greece is very limited due to the unavailability of valid, and reliable assessments. To support teachers' evaluation and professional development in Greece, valid assessments that measure teachers' classroom practice and capture teachers' strengths, and areas in need of improvement are urgently needed. The current study presents the Greek translation and initial validation of the Classroom Strategy Assessment System (CSAS), a multi-rater, multi-source observational assessment of teachers' evidence-based instructional and behavior management strategies. Trained school administrators observed 31 elementary school teachers (age range of students 6-12 years), three times each for 30 minutes in Greek Language Arts and mathematics lessons. Internal consistency, test--retest reliability, and interobserver reliability of the translated Greek CSAS were examined. Results revealed strong internal consistency, adequate test-retest, and interobserver reliability, and support the use of the CSAS in Greek classrooms. Overall, findings indicate that Greek teachers were rated as utilizing evidence-based classroom practices, but rates for some practices were lower than recommended by the literature. Implications for research and professional development are discussed.