This study examines the effectiveness of content-based language teaching (CBLT) in teaching English as a foreign language (TEFL) contexts, focusing on its impact on language proficiency and subject matter learning. CBLT integrates language instruction with academic content, aiming to enhance both linguistic skills and cognitive abilities simultaneously. The research employed a mixed-methods approach across multiple TEFL settings, including primary and secondary schools, to evaluate CBLTs efficacy. Quantitative data from pre-tests and post-tests, supplemented by surveys, measured improvements in language proficiency and academic achievement among students exposed to CBLT compared to traditional methods. Qualitative methods, such as classroom observations, teacher interviews, and student focus groups, provided deeper insights into instructional processes and learner experiences. Findings indicate significant enhancements in students language proficiency across speaking, listening, reading, and writing skills in CBLT classrooms. Academic achievement in subjects like science, mathematics, and social studies also showed improvements, demonstrating the effectiveness of integrating language and content learning. Moreover, CBLT fostered higher levels of learner engagement and motivation by linking language skills with practical applications in academic contexts. Teacher perspectives highlighted the benefits of CBLT in promoting interdisciplinary learning and addressing diverse student needs, albeit with challenges related to curriculum integration and varying language proficiency levels. The study underscores the potential of CBLT to promote inclusive education by providing equitable access to language and content learning for all students. These findings contribute valuable insights to educational practices, emphasizing the importance of integrating language instruction with subject matter learning to enhance educational outcomes in TEFL contexts globally.