A stereoscopic image display system includes a three-dimensional (3D) image signal generator, a display panel, a timing controller, a data driver, and a gate driver. The 3D image signal generator generates left-eye data and right-eye data on the basis of an image signal outputs the left-eye data and the right-eye data to the timing controller. The timing controller outputs the left-eye data and the right-eye data having a first frequency to the data driver in a first mode and outputs left-eye frame data and right-eye frame data having a second frequency to the data driver in a second mode. Two pixels, which are respectively connected to an i-th gate line and an (i+1)th gate line among the gate lines and to a same data line among the data lines, are operated with the same driving time in the first and second modes.