Bias is communicated via the "hidden curriculum"--the vehicle for the unspoken academic, social, and cultural messages that are communicated to students while they are in school. Revealing the hidden curriculum in English language textbooks (ELTs) entails an analytical and holistic approach to the content of the text and images appearing in school textbooks by connecting corresponding examples of subliminal bias which may be many pages apart. This article reviews existing Japanese and international literature on the gender bias created by the hidden curriculum before going on to present a Japanese case study of an ELT in widespread use in Japanese public junior high schools. It was found that while males and females are represented equally in terms of quantity, there exists a remarkable subliminal gender bias that affects young learners' worldviews of female and male roles in society.