A display device includes a controller to generate a start frame control signal having a first level in an active period and a second level in a blank period, a load signal toggling between the first level and the second level in the active period and having the second level in the blank period, and a data signal including image data in the active period and a training pattern in the blank period, and a data driver to recover the image data from the data signal based on an internal clock signal to provide display pixels with data voltages in the active period, and to perform a training operation for the internal clock signal using the training pattern in the data signal when both of the start frame control signal and the load signal are maintained as the second level for more than a reference time in the blank period.