Introduction: With an increase in the number of mentally demanding jobs, as well as the increase in work performed while sedentary, there is a growing imbalance in the use of body resources. This often results in an increase in fatigue in the working population. The diversity of the workforce is also increasing, whereas physiological differences based on culture are important to consider. The objective of this study was to identify the differences in the levels of fatigue in the workplace experienced by Asian and Western workers in mentally demanding jobs. Method: Eight Asian and eight Western participants completed an observation-based study. Each participant was observed for four hours in their workplace while they were working on highly mentally demanding work-tasks either computer programming or mathematical simulations. To balance the effect of time, half of the participants from each ethnic group were observed in the morning session and the other half in the afternoon session. Perceived fatigue was measured every 30 min using the single dimensional Borg and multidimensional SOFI scales. Workload was measured using NASA-TLX, and as a change in resting heart rate. Result: Ethnicity and time interacted to significantly affect the perceived fatigue measured by Borg (F (9,126) = 2.03, p = 0.0412) and SOFI (F(9,126) = 3.28, p = 0.0013) scales. Asian participants reported significantly higher workload measured by NASA-TLX scores (F(1, 14) = 3.68, p = 0.0024) and change in resting heart rate (F(1,14) = 7.77, p = 0.0145) was measured higher compared to Western participants. Unlike fatigue, no significant interactions were observed between time and ethnicity to affect either NASA-TLX scores or change in resting heart rate. Post-hoc analyses show that the rate of fatigue was higher for Asian participants. Correlations between the dependent variables were significant (p < 0.0001), with a stronger correlation identified for Asian participants. Conclusion: As compared to the Western participants, Asian participants reported higher values in all dependent measures, including fatigue in both scales, NASA-TLX scores, and change in resting heart rate. Relevance to industry: The significant growth in white-collar as well as mentally demanding jobs requires more cognitive resources, while reducing physical activities. The consequences of the imbalances in the use of body resources have yet to be studied. This study has been designed to investigate the issues of imbalance in the workplace. (C) 2016 Elsevier B.V. All rights reserved.