This study proposes a theoretical model from a collectivism perspective to examine the factors affecting buyers’ motivation to engage in auctions through online group-buying websites. The model was tested using the data collected from 218 buyers participating in a Taiwan online group-buying website. The results show that the intention to participate in online group-buying auctions significantly affected group-buying behavior, while conformity, attitude, and collective efficacy had significant influences on the intention to participate in online group-buying auctions. The results also indicate that trust in websites, trust in auction initiators, and trust in buyers are the antecedents of attitudes toward online group-buying auctions. Implications for theory and practice and suggestions for future research are discussed.