Rejection of periodic signals has been a subject of great interest in control theory and engineering applications. Periodic disturbances are usually present in mechatronic, hydraulic and electronics systems, between others. This paper proposes a resonant observer-based control for periodic signal rejection. The observer includes, in an embedded way, an internal model of the disturbance that is based on its harmonic decomposition. The resulting disturbance estimation is used by a control law that cancels the periodic disturbance term while controlling a specified tracking task. The proposed scheme lets the control designer to address the disturbance estimation and tracking problems separately. Experimental results, on a mechatronic test bed, show that the proposed resonant observer-based control successfully rejects periodic disturbances.