Purpose <p>Active vibration control typically requires mathematical modeling of the plant, which increases development costs and burdens for designers. This study develops a novel model-free vibration controller that can be designed without using any models or parameters of a real controlled object.</p> Methods <p>This study proposes a new model-free fuzzy sliding mode vibration controller based on a virtual controlled object (VCO). The key idea is the combination of the VCO-based model-free controller design, sliding mode control (SMC), and fuzzy adaptive compensation for chattering elimination. By inserting the VCO, defined as a single-degree-of-freedom (SDOF) structure, between a real controlled object and an actuator, the model-free control system is realized. According to a simple inequality-based condition, the VCO parameters are specified to enable the design of an active vibration controller without requiring any models or parameters of the controlled object. This design scheme is directly applied to the sliding mode control theory, and convergence is analyzed using a Lyapunov function technique. To eliminate the chattering phenomenon, a fuzzy-inference-based compensation is introduced. Considering variations in the switching function, this fuzzy inference modifies the nonlinear switching input online to prevent chattering while ensuring the state trajectory rapidly converge to the sliding surface.</p> Results <p>Simulation verifications are conducted with various mechanical structures, including time-varying system. The present approach achieves good vibration control performance without causing the chattering phenomenon. Comparative study reveals the advantage of the present approach over the conventional model-based controller design from the viewpoint of its simple design procedure and robustness.</p> Conclusion <p>The proposed model-free fuzzy SMC provides sufficient damping performance and excellent robustness, showing its practical usability.</p>