Gender bias in teaching materials may influence students' development and contribute to social inequalities. This study investigates possible gender bias in a newly published English textbook series in Vietnam. Holding gender as a social construct, the research uses a multimodal critical approach to examine language and ideological systems. The results show despite some effort for gender equity, the making of textbooks in today's Vietnam is still affected by patriarchal Confucian values. Males inhabit bigger verbal space and have more social properties. Females are portrayed as less independent; their choices are more limited, and with less resources. Textbook author interviews show the writing was influenced by conscious and unconscious bias, but they agreed gender equality is important, although male domination beliefs still seem to be deeply ingrained in the society. The study raises questions on challenging the status quo and creating a new cultural narrative for women's rights recognition and enactment.