This study developed and tested the impact of hallyu 4.0, social media, and consumer ethnocentrism on the decision to purchase Korean products of Generation C in Vietnam. Both qualitative and quantitative methodologies were utilized in this study. Qualitative research was first carried out with in-depth interview, conducted to derive measurement items for the interested constructs. Quantitative research used cross-sectional field design by pilot study and official study. The model was tested and developed using data collected by questionnaires, from a sample of 575 respondents, by both electronic and paper surveys with non-probability and convenience sampling techniques. SPSS 20 and AMOS 20 software were employed to analyze the data. The results of structural equation modeling showed that hallyu 4.0, social media, and consumer ethnocentrism influenced the intermediates variables: subject norms, trust, attitude and behavioral intention and influenced purchase decision. The hallyu 4.0, social media, and consumer ethnocentrism are independent variables. They impact purchase decision through mediating variables such as trust, subjective norms, attitude and behavioral intention. Social media influences not only to trust but also to subjective norms. Subjective norms influence on purchase decision. This study also discovers an interesting fact that trust and attitude variables have an impact on behavioral intention and purchase decision.