Abstract: Recently, the topic of wireless sensor networks has become a fast-growing research area. In wireless sensor networks, sensor location plays a crucial role in many applications. The global positioning system (GPS) solves the problem of localization in outdoor environments, but it is not suitable for wireless sensor networks. Having a GPS receiver on every sensor is always costly and not feasible. So, in the past, there are many localization procedures have been proposed in the literature. In this paper, a distributed, accurate and reliable Voronoi diagrams based localization scheme (VBLS) is introduced, which makes use of received signal strength indicator (RSSI) from anchors. First, VBLS sorts received signal strength indicator in descending order. Then unit disk graph is used to calculate the Voronoi area of anchors in turn. Finally, the overlapping region of different anchors' Voronoi area is identified as the possible region where sensor resides in. This work is compared via simulation with two other range-free localization schemes (W-Centroid and Centroid) to show the efficiency of VBLS. For random anchor placement, VBLS outperforms Centroid scheme and W-Centroid scheme significantly, estimation error decreases by 18% and 13%, respectively. For uniform anchor placement, VBLS gets a gain of 7% decrease and 2% increase of estimation error, respectively.