||The present study aimed to investigate the effect of an LED lighting on endocrine and autonomic nervous system activity during sleep. In a within‐subject experimental design, participants, ten healthy male students, took a 6‐h sleep from 0:00–6:00 am in an environmentally controlled room during which they were exposed to an LED lighting of approximately 50 lx for 90 min from 1:30–3:00 am, whereas there was no light exposure under the control condition. Compared to the control condition, the heart rate (HR) during light exposure, 1 h before awakening, and 1 h after awakening, was significantly higher under the light exposure condition. Salivary melatonin under the light exposure was significantly higher than that under control condition, meanwhile there was no difference in salivary cortisol secretion. Light exposure during sleep may enhance the sympathetic nervous system activation but not give an impact on the hypothalamic–pituitary–adrenal pathway during sleep.