Abstract-Temporary link failures and route changes occur frequently in mobile ad hoc networks. Since TCP assumes that all packet losses are due to network congestion, TCP does not show satisfactory performance in ad hoc networks. In this paper, we propose a simple and new mechanism called TSR, TCP-aware Source Routing, which can improve TCP performance in mobile ad hoc networks. By reducing the number of invalid route, TSR minimizes TCP?s consecutive timeouts. In our simulation study, TSR achieves up to 50% TCP performance improvement without requiring any modification of TCP stack in end systems.