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Abstract To reject the disturbances of the nonminimum‐phase systems, the generalised dual‐filter disturbance observer is proposed. The conventional disturbance observer methods inevitably lead to nonminimum‐phase systems' instability. To stabilise the system, the forward plant and dual filters are introduced. The stability constraints are transferred to the dual filters. Based on any stable designs of the close‐loop controller, the dual filters can be easily designed. The simulations effectively verify that the disturbance rejection performances of the proposed method are triple those of the closed‐loop nonminimum‐phase system, and the original system's tracking capabilities and stability margins are few affected.