Maintainability is an important design characteristic of a mechanical system, making various maintenance activities easier. Easily maintainable equipment gives industrialists a real advantage over competitors. Implementing such equipment is often complex and difficult for design engineers to take into account uncertainties and imprecisions at the design stage. There are several tools that can be used to assess maintainability, but these have been more developed as traditional tools. This article aims to propose a new approach to integrating maintainability into the design phase of mechanical systems based on fuzzy logic, which is built from human knowledge to support design engineers. Indeed, this method allows us to evaluate maintainability in the design phase according to its attributes, which are translated into linguistic variables. Our case study demonstrates the effectiveness of the method presented in this work during the design phase and evaluating maintainability based on attributes such as standardization, disassembly, and accessibility.