The emergence of Wireless Sensor Networks brought many benefits in different application domains such as collaborative tasks, lower costs, equipment's autonomy and higher tolerance to failures. These advantages made the number of applications that use this kind of network grow in the past few years. Meanwhile, the possibility of employing these systems to trace the movement of an object, which can be part of the network itself, is of great utility. The present work aims at the study and development of a localization system of mobile nodes for Wireless Sensor Networks. Different methods to obtain the distances between network nodes are studied and received signal strength algorithms are developed to synthesize the data and to show the location of the nodes. Finally, simulations and experiments are presented in order to analyze the viability of the developed proposal.