This paper introduces a new approach based on fuzzy logic techniques for microwave circuit design. The Fuzzy Logic System (FLS) is constructed using data pairs generated from an EM simulator. A 3-pole microstrip filter is used to demonstrate the concept. The FLS is employed as a design tool to directly synthesize the filter physical dimensions for a required filter response. Theoretical results for three filters having different bandwidths are presented to demonstrate the validity of the proposed approach.