Localization is one of the main challenges in Wireless Sensor Networks. It is performed to determine the location information of sensor nodes in the network. When the sensors collect data and report events, it is important to know the origin of data and events. In this work, a nature-inspired population based optimization algorithm called Group Search Optimizer (GSO) is proposed for locating sensor nodes in a distributed WSN environment. WSN localization is formulated as a nonlinear optimization problem and solved using GSO. Performance evaluation of GSO based localization algorithm is carried out through simulations.