This study investigated the effects of self-awakening on daytime sleepiness. Eleven undergraduate and graduate students without the habit of self-awakening participated. They were instructed to follow their usual sleep-wake schedule at home during the experimental weeks and were required to awaken at their usual time by themselves every morning for one week without the aid of an alarm (self-awakening condition) or in response to a telephone call from the experimenter every morning for another one week (forced-awakening condition). On the last day of each week, daytime tests were conducted in the laboratory. The participants would arrive at the laboratory 2 h after awakening, and 1 h later, they performed the auditory simple reaction time task, the digit-symbol substitution task, the letter cancellation test, and the multiple sleep latency test, and assessment of sleepiness, fatigue, comfort, and work motivation every 2 h. In the week when the participants underwent the self-awakening condition, self-awakening had a higher success rate (82%) than failure rate (18%) on the seventh day. In comparison with forced-awakening, self-awakening resulted in an improvement in subjective fatigue; however, sleepiness did not deteriorate.