This paper is concerned with the state interval estimation for discrete-time linear switched systems affected by unknown but bounded disturbances and measurement noises. A novel interval estimation method is proposed by integrating robust observer design with zonotopic techniques. By introducing L ∞ technique into observer design, the proposed method is effective in attenuating the influence of unknown disturbances and noises, and improving the accuracy of interval estimation. Based on the designed observer, the state interval estimation can be obtained by using zonotopic analysis. Finally, the feasibility and effectiveness of the proposed method are illustrated by numerical simulations.