AbstractThis paper is concerned with the robust guaranteed cost control problem for networked control systems (NCSs). The plant considered is an uncertain linear discrete‐time system, where the communication limitations include packet‐loss and signal transmission delay. Our purpose is to design a robust state‐feedback guaranteed cost controller such that the resulting closed‐loop system is robustly stable, and a specified quadratic cost function is upper bound for all admissible uncertainties under such communication limitations. A model of NCSs is established which contains two additive delay components, one being a known constant, and the other unknown constant. By introducing a novel Lyapunov‐Krasoviskii function with the idea of delay partitioning, new sufficient conditions for the existence of guaranteed cost controllers are proposed. Numerical examples are provided to demonstrate the usefulness of the developed theory. Copyright © 2010 John Wiley & Sons, Ltd.