Several atypical hierarchical routing protocols have been proposed among which grid-based routing protocols are an efficient way of disseminating data towards a mobile sink. The network is partitioned into a virtual equal-sized grids. The proposed protocol, Mode-Switched Grid-based Routing (MSGR) for Wireless Sensor Networks selects one node per grid as the Grid Head. The routing path to the sink is established using Grid Heads. Grid Heads are switched between active and sleep modes alternatively. So, not all Grid Heads take part in the routing process at a time. This saves energy of Grid Heads and improves the network lifetime. The proposed method builds a routing path using each active Grid Head leading towards the sink. The routing path changes only for some Grid Head nodes whenever the mobile sink moves to a different grid. Data are directly transmitted through this path to the sink.