— We propose a fuzzy-based decision-making mechanism for selecting data dissemination protocols in wireless sensor networks (WSNs). Its goal is to select the most efficient protocol considering network performance and application-specific requirements. The mechanism relies on performing simulations and on defining and executing a twotier fuzzy system. First, well-known WSN protocols are simulated over different scenarios and application requirements to feed a knowledge base. Then, a set of fuzzy systems are built based on the simulation results. A methodology for guiding the building of the knowledge base was developed. A case study is described to validate the mechanism and demonstrate its employment and usefulness.