In the wake of China's educational internationalization policy and the technological shifts post-COVID-19, the mode of educational globalization has undergone significant transformations. In this context, this study investigates the academic English writing challenges of Chinese international high school students (CIHSSs) in a blended English as a foreign language (EFL) and English as a second language (ESL) learning environment. Drawing on Vygotsky's sociocultural theory and prior research, the study examines the specific hurdles CIHSSs face in academic writing. Previous research has highlighted various difficulties in academic English writing for international students; however, a significant research gap exists concerning high school students, especially in blended learning context settings. To fill this gap, this qualitative case study explores CIHSSs’ English language learning experiences, focusing particularly on their academic writing challenges in a blended EFL and ESL context. Through semi-structured individual interviews with three CIHSSs, the study conducts a thematic analysis to identify key challenges across five areas: cultural differences, unfamiliarity with academic norms, language proficiency limitations, communication barriers, and technological adaptation issues. The findings emphasize the importance of communication, especially peer support and collaborative learning, underlining the need for effective English language learning strategies (ELLSs). These insights are vital for educators and learners to navigate the complexities of blended EFL and ESL learning environments effectively.