In this paper a novel Active Vibration Control (AVC) strategy based on fractional-order calculus is developed. A fractional-order Positive Position Feedback (PPF) compensator is proposed to overcome the limitations of the commonly used integer-order PPF such as: frequency spillover, amplitude amplification in the quasi-static region of the closed-loop response, and difficult tuning in multi-mode control. Tuning parameters of the controller are obtained by optimizing both magnitude and phase response of the controlled plant. Results are shown by comparing performances of the standard integer-order PPF and the optimized fractional-order PPF, both on a simple 1-DOF plant and on measured frequency response data from a rectangular carbon fibre composite plate.