Vulnerability assessment is one of the most effective tools for the quality protection of karst aquifers. In the COP method, three essential factors, i.e., karstification process (K), atmospheric conditions (A), and tectonic (T) of the KARSTLOP method, are not considered despite being important factors in karstic aquifer vulnerability. This study aims to develop a new method to obtain the vulnerability map for karst aquifers based on the COP method and the factors used in the KARSTLOP method. The new method, namely COP*KAT, considers K, A, and T factors in the COP method using fuzzy logic. A comparison of microbial and nitrate contamination indices for livestock and agriculture land use, respectively, to the distribution of vulnerability classes for three springs in the study area (Dorfak region, Iran) reveals the more efficient performance of COP*KAT compared to COP in vulnerability analysis.