Guanxi is known to be an important feature of Chinese society, and guanxi position plays a critical role in social commerce in contemporary societies. The purpose of this study is to theorize and examine how the Confucian philosophy-guanxi position influences the purchase intention on social media. The purchase-decision involvement (PDI) is introduced to gain insight into its moderating effects on purchase intention (PI) from four different guanxi positions. We conducted this study in Ho Chi Minh City, Vietnam by making online surveys, and 370 responses were collected from 400 questionnaires issued. The results show that interpersonal guanxi position does work in social commerce, and purchase-decision involvement (PDI) moderating has been considered to be an important contingent factor while a consumer is facing a purchase-decision making. Through empirical evidence, we confirm that the buyer-seller guanxi position does affect seller influence effectiveness (SIE) and purchase intention (PI). Besides, B-S guanxi positions might affect the guanxi facets, SIE and PI. This study provides the interpersonal selling practices, and help clarify how a buyer’s perception of B-S guanxi influences SIE and PI while the buyer is encountering commercial messages on social media. Moreover, this study offers several practical implications for developing successful businesses in social commerce. Keyword: Guanxi, Social Media, Social Commerce, Purchase Intention, Purchase-Decision Involvement, Seller Influence Effectiveness.