By investigating Vietnamese English learners' perspectives on influential cultural factors and barriers these factors bring to the development of learner autonomy, this study seeks to draw attention to proper consideration of the host cultural values in importing and implementing Western educational theories. A phenomenological approach was employed, and qualitative data were collected from in-depth interviews with 15 English majored students from a public university in the Mekong Delta. Using Hofstede et al.'s (2010) six-dimensional model of cultural differences as a theoretical framework, the study reveals that all the six dimensions, at different levels, hinder the development of learner autonomy. The study also uncovers cultural assimilation - a state in which individuals perceive a certain cultural characteristic as their personality traits without any adjustment, corresponding to the Restraint factor. These results emphasize the significance of cultural analysis and imply the need for constructing a culturally appropriate pedagogy to promote learner autonomy. The paper concludes by discussing some possible directions for further research in the field.