A display device includes: a display panel and a panel driver for driving the display panel during a plurality of driving frames whose frequencies are varied. Among the driving frames, a first driving frame having a first frequency includes a first write period, and a second driving frame having a second frequency lower than the first frequency includes a second write period and a variable blank period. The panel driver includes a data driver and a driving controller. Each of the first and second write periods includes N horizontal periods (N is an integer number equal to or greater than 1), each of the N horizontal periods has a first duration, and each of the first and second write periods has a second duration corresponding to N times of the first duration. The driving controller applies a training synchronizing signal to the data driver during the variable blank period.