What will happen if a new tool is introduced to different cultures? What if the tool can potentially bridge those cultures? Will it be used in the same way across cultures and contribute to a decrease in cultural differences? Or will it be used in culturally appropriate ways and eventually integrated into preexisting cultural practices? To answer these questions, we predicted and examined cultural differences in the use of Facebook focusing on social networks. In support of the prediction, the present work found that users in individualistic cultures had more ego-centric networks (i.e., members of networks were connected via the self) than users in collectivistic cultures. The results were consistent across a two-culture comparison and a multicultural analysis across 49 nations. Additional findings suggest that (a) living in individualistic/collectivistic cultures are closely linked to these differences in social networks and (b) the individualism– collectivism may have stronger influences than ecological factors that gave rise to it.