<p><strong>Background:</strong> Student performance determines learning achievement and how students absorb lessons in class. One of the factors that cause student performance to decline is physical fatigue, which arises because of the classroom’s physical environment that does not support the teaching and learning process. <strong>Purpose:</strong> This study was conducted to determine the relationship between classroom’s physical environmental conditions and fatigue among high school students. <strong>Methods:</strong> The study design used was cross-sectional. Data collection included measurements of physical environmental parameters (humidity, temperature, lighting, noise, air flow, ventilation, temperature control, room capacity, room area ratio per person, and school location) and measurements of fatigue among students using the Subjective Self Rating Test in the form of questionnaire. Total sample was 448 students in 10 private high schools, with inclusion criteria: the students are not sick in the last two weeks and 10th and 11th grade students from 10 private high schools. <strong>Results:</strong> The research showed classroom’s physical environmental factors that affect fatigue among student’s included temperature, relative humidity, air flow, and air conditioner. While the most dominant indicator that was related to the occurrence of students’ fatigue was sex. <strong>Conclusion:</strong> Further research is needed on other factors that may cause fatigue among students in the classroom to support the conclusion of this research.</p>