An image pickup system includes a stereoscopic endoscope including image pickup optical systems having a parallax therebetween and a first image pickup device and a second image pickup device, and a processor including a first photometric measurement section configured to photometrically measure a luminance value of a first image pickup signal related to the first image pickup device, a second photometric measurement section configured to measure a luminance value of a second image pickup signal related to the second image pickup device, and a control section including a threshold value comparison section configured to compare the luminance value with a threshold value. When the luminance value of either one of the first image pickup signal and the second image pickup signal exceeds the threshold value, the image pickup system performs light adjustment control of a light source based on a photometric value of the other image pickup signal.