This study examined the relationships among Cultural Intelligence (CQ), Classroom Management (CM), and Teaching Effectiveness (TE) among foreign teachers in Thailand using a cross-sectional, multi-source research design. Data were collected from 150 foreign teachers and their students across international and bilingual schools, using validated instruments that demonstrated strong reliability and construct validity. Correlation and regression analyses revealed that all four CQ dimensions significantly predicted teaching effectiveness, with classroom management emerging as the strongest predictor. Mediation testing using Hayes’ PROCESS Model 4 indicated that CM partially mediated the CQ-TE relationship, with 44% of CQ’s total effect transmitted through CM. Findings suggest that cultural intelligence enhances teaching effectiveness primarily through its translation into culturally responsive management behaviors. Demographic analyses revealed that years of teaching experience in Thailand had a significant impact on CQ, CM, and TE, whereas gender, school type, and grade level showed no significant differences. These results highlight the significance of intercultural competence, effective classroom management, and sustained cultural immersion in influencing the instructional performance of foreign teachers. The study offers practical implications for teacher recruitment, induction, and professional development, emphasizing CQ-building initiatives, management-focused training, and structured mentorship to support cultural adaptation and integration. Recommendations for future research include expanding the sample across regions and employing longitudinal or mixed-methods designs to track the development of CQ and CM over time..