The speed control problem of a time-delay DC motor system is proposed because the control performance can severely deteriorate under uncertain delay time information. Since most of existing delay compensators require exact system parameters and delay time information, the performance improvement has been limited under delay time uncertainty. The proposed method incorporates a disturbance observer on the slave side of the system with a communication disturbance observer that does not require the delay time information for generating a predicted output signal. The effectiveness of the proposed algorithm is tested through comparative simulations and experiments using a testbed system under large delay time uncertainty.