Existing literatures show that deploying fixed relay infrastructure with stable interconnections can help to improve network connectivity. However, fixed relay infrastructure is inflexible and could be costly to deploy over large area. In this paper, we study the effectiveness of mobile relays in improving network connectivity in both Random Waypoint and Manhattan mobility models. Through extensive simulation, it is observed that mobile relays help to effectively improve the network connectivity, prolong the mean contact duration and reduce the number of network partitions. The mobile relay approach is also compared with the alternative approach of increasing node density. Through the simulation results, it is observed that mobile relay approach is far more effective than the alternative approach. Furthermore, we observe that the expected contact duration remains brief even with the mobile relays and discuss the implication of this observation in the design of routing protocols and clustering algorithms.