This note combines an adaptive frequency estimation scheme with a fractional-order controller for unknown biased sinusoidal disturbance rejection. The disturbance is estimated via an adaptive orthogonal signals generator based on a third-order generalized integrator. A fractional-order controller is designed which guarantees the closed-loop stability of the system if the location of the plant frequency response, at the estimated frequencies, lies in an half-plane passing through the origin of the complex plane.