A delay cell includes a first inverted transistor pair, a second inverted transistor pair and a plurality of delay units. The first inverted transistor pair is used to receive an input signal. The second inverted transistor pair is electrically cross-coupled to the first inverted transistor pair and cross-controlled by the first inverted transistor pair. The delay units are cascaded between the first inverted transistor pair and between the second inverted transistor pair, thereby providing a plurality of signal propagation delays sequentially, wherein the input signal is delayed for a pre-determined time by the first inverted transistor pair, the second inverted transistor pair and the delay units which are operated sequentially, thereby creating an output signal corresponding to the pre-determined time. A digitally controlled oscillator including the aforementioned delay cells is provided.