This chapter analyzes how the Internet enables social and political mobilization of diasporic communities. Two diasporic communities-the Eritreans and the Iranians-form the empirical basis. The Eritrean diasporic community has used the Internet in their fight against Ethiopia and in their efforts to establish Eritrea as an independent country. The Iranian diasporic community used social networking, blogging, and other methods to politically mobilize amongst themselves in the host society and to mobilize their fellow countrymen in their homeland in the recent 2009 elections. The case studies illustrate how the Internet enables political mobilization that transcends time and space. Yet, the success of political mobilization depends on the diaspora's relationship with the homeland's government, their ability to create linkages, and their power relations.