Content and language integrated learning (CLIL) is an educational approach teaching students content knowledge in a second language. With its dual foci, CLIL is becoming increasingly popular, yet, there is still a dearth of CLIL textbooks in the market and a necessity for CLIL textbooks analysis. This paper presents a study on Unlock (a set of textbooks used in an academic context) under the framework of 4C-s in CLIL, specifically, content, cognition, communication and culture, with data collected through content analysis, corpus-based analysis, questionnaires and interview. Findings reveal that Unlock covers a wide range of common topics in IELTS, presents variety in cognition level in Bloom’s taxonomy, takes into account both English cultural and intercultural factors. However, in communicative competence, compared with linguistic, sociocultural and discourse competence, Unlock relatively ignores developing learners’ strategic competence.