Objective: To evaluate the effects of astaxanthin on the sense of fatigue occurring in daily life and to investigate the relationship of the fatigue-reducing effect with the antioxidative potential. Method: A 12-week, randomized, placebo-controlled, parallel-group study was conducted. After screening for eligibility, 39 subjects with fatigue were assigned to 2 groups. The astaxanthin group received 12 mg of astaxanthin and 20 mg of tocotrienol, while the control group received 20 mg of tocotrienol alone. All subjects took Uchida-Kraepelin performance tests as mental loading and cycled using a bicycle ergometer as physical loading in Weeks 0, 4 and 8. A visual analog scale (VAS) of perceived fatigue was performed before and after loading. In Weeks 0 and 8, a Profile of Mood States (POMS) questionnaire was performed. The biological antioxidant potential (BAP) was measured with blood samples taken at the screening and in Week 12. Results: Thirty-eight subjects completed the study. Intent-to-treat (ITT) analysis revealed that the sense of fatigue after both physical and mental loading was significantly lower in the astaxanthin group than in the control group in Week 8. The change in Friendliness in POMS was significantly higher in the astaxanthin group than in the control group in Week 8. No significant differences were observed in the change rate in the BAP value in Week 12 between the astaxanthin group and control group. Conclusion: Astaxanthin reduced the daily sense of fatigue caused by both mental and physical loads. No increase in BAP was, however, observed in subjects receiving astaxanthin.