Mobile Ad hoc Networks (MANETs) are a key part of the ongoing evolution of wireless communications. MANETs are a collection of wireless mobile nodes that dynamically form a temporary wireless network without an infrastructure. The design of an efficient and reliable routing scheme and Quality of Service (QoS) support for MANETs is a major challenge. Unlike traditional routing schemes that seek only single path, multipath routing allows the establishment of multiple paths for routing between a source-destination pair. Multipath routing exploits the resource redundancy and diversity in the underlying network to provide benefits such as fault tolerance, load balancing, capacity aggregation and the improvement in QoS metrics such as delay. In the first part of the thesis, a multipath routing scheme, referred to as Shortest Multipath Source (SMS) routing based on Dynamic Source Routing (DSR) protocol is proposed. The mechanism has two novel aspects compared to other on-demand multipath routing schemes: it achieves shorter multiple partial-disjoint paths and allows more rapid recovery from route breaks. This scheme addresses the problem of wireless broadcast storms by simple hop count mechanism. The performance differentials are investigated using Network Simulator version 2 (NS-2). Results show the superiority of SMS under certain scenarios in terms of goodput of up to 85% and end-to-end delay of up to 99% when compared to the competing schemes. Although SMS is designed to find multiple shorter routes, these routes have no information about the network traffic or application requirements. The second aspect of the thesis addresses QoS support. Two novel capacity-constrained routing schemes based on SMS, which allow nodes to depend on their estimation of the residual capacity to make correct admission control decisions, are presented. The performance evaluation demonstrates the merits of the proposed schemes with a 20% increase in goodput while end-to-end delay is reduced by 47% and the necessity of QoS-aware multipath routing schemes in Mobile Ad hoc Networks becomes more apparent.