A Mobile Ad hoc Network (MANET) consists of a group of mobile nodes that can move abruptly in and out the network. MANET has several special specifications including, non-fixed infrastructure, the absence of a central administration, limited bandwidth, and limited energy. Merging two MANETs is a situation that can occur frequently because of mobility. Due to the nature of MANET, it is vulnerable to attacks such as Denial of Service (DoS). In this paper a proposed method called Merging Using MrDR (MUMrDR) is used to merge two MANETs based on the Monitoring, Detection, and Rehabilitation (MrDR) method to mitigate such attacks. By adopting this method, it will be possible to detect DoS attacks when merging two MANETs, thereby maintaining network operations.