In the last decade, a great deal of research has been addressed to the input–output linearization problem for non-linear time-delay systems. However, the input-state linearization problem got much less contributions. In this paper, the input-state linearization problem for a class of single-input non-linear time-delay systems is studied. The problem is solved locally by searching a linearizing output with a full relative degree. Necessary and sufficient conditions are given for the existence of such an output which yields a solution to the full linearization problem.