This book constitutes the thoroughly refereed proceedings of the fourth International Conference on Mobile Networks and Management, MONAMI 2012, held in Hamburg, Germany, in September 2012. The 15 revised full papers presented were carefully selected and reviewed from numerous submissions. In addition two well-received workshops are presented: the second MONAMI Workshop on Smart Objects and the first Open Connectivity Services Workshop, organized in cooperation with the EU FP7 SAIL project. All in all, 25 papers were orally presented at the conference. The papers are organized in five topical sections: mobile networks, heterogeneous networks, wireless communications, smart objects and IoT applications, and future networks.