Sleep is associated with specific alterations of brain physiology, including oscillatory and non-oscillatory neuronal activations, and functional connectivity. These are thought to be of crucial importance for sleep-dependent psychological processes, including memory consolidation, dreaming, and consciousness states. Non-invasive brain stimulation has the potential to alter respective physiology, and thus might affect respective processes. An overview about the application of transcranial electrical stimulation (tES), including transcranial direct and alternating current stimulation (tDCS and tACS), to modulate sleep-dependent processes will be given. This includes modulation of memory consolidation, modulation of sleepiness and fatigue, and consciousness states during dreaming. The results of respective pilot studies suggest that tES is a promising and emerging tool to alter respective functions.