Arousal and sleep are fundamental physiological processes, and their modulation is of high clinical significance. This study tested the hypothesis that total sleep time in humans can be modulated by the non-invasive brain stimulation technique transcranial direct current stimulation (tDCS) targeting a 'top-down' cortico-thalamic pathway of sleep-wake regulation. Nineteen healthy participants underwent a within-subject, repeated-measures protocol across five nights in the sleep laboratory with polysomnographic monitoring (adaptation, baseline, three experimental nights). tDCS was delivered via bi-frontal target electrodes and bi-parietal return electrodes prior to sleep (anodal 'activation', cathodal 'deactivation' and sham stimulation). Bi-frontal anodal stimulation significantly decreased total sleep time, compared to cathodal and sham stimulation. This effect was location specific. Bi-frontal cathodal stimulation did not significantly increase total sleep time, potentially due to ceiling effects in good sleepers. Exploratory resting-state EEG analyses prior to and after the tDCS protocols were consistent with the notion of increased cortical arousal after anodal stimulation and decreased cortical arousal after cathodal stimulation. The study provides proof-of-concept that total sleep time can be decreased by non-invasive bi-frontal anodal tDCS in healthy humans. Further elucidating the 'top-down' pathway of sleep-wake regulation is expected to increase knowledge on the fundamentals of sleep-wake regulation and to contribute to the development of novel treatments for clinical conditions of disturbed arousal and sleep.Neuropsychopharmacology accepted article preview online, 04 May 2016. doi:10.1038/npp.2016.65.