In today's modern society, an increasing number of people have developed sleep-related problems, represented by sleep loss and chronic insomnia. These are due to drastic changes in living conditions such as prolonged work time, increased shift working, and various socio-psychological stresses. Sleep problems have been reported to strongly associate with emotional dysfunction in humans. Sleep loss cause not only daytime sleepiness and psychomotor impairment, but also emotional instability, anxiety and confusion, and chronic insomnia increases vulnerability to mood and anxiety disorders. Recent studies have revealed some of the neural basis of emotional regulation by sleep. For instance, continuous and accumulating sleep debt experienced in daily living could interfere with the functional regulation of the amygdala by ventral anterior cingulate cortex. And consequently this can induce an overreaction of the amygdala to negative emotional stimuli. Sleep-related mood disturbances may, in part, be attributable to the neural basis of emotional instability during sleep debt. In this text, recent findings on the functional linkage between sleep and emotional regulation have been reviewed.