Prior studies investigating business-to-consumer e-commerce have focused predominantly on online shopping by individuals on their own, although consumers often desire to conduct their shopping activities with others. This study explores the important, but seldom studied, topic of collaborative online shopping. It investigates two design components that are pertinent to collaborative online shopping support tools, namely, navigation support and communication support. Results from a laboratory experiment indicate that compared to separate navigation, shared navigation effectively reduces uncoupling (i.e., the loss of coordination with one's shopping partner) incidents per product discussed and leads to fewer communication exchanges dedicated to resolving each uncoupling incident, thereby enhancing coordination performance. Compared to text chat, voice chat does not help reduce the occurrence of uncoupling, but likely increases the efficiency in resolving uncoupling. The results further show that shared navigation and voice chat can significantly enhance the collaborative shoppers' perceptions of social presence derived from their online shopping experiences. The interaction effect on social presence implies that the benefit of shared navigation is higher in the presence of text chat than in the presence of voice chat.