Someone will have a greater risk of experiencing heat strains if working at a workplace exposed to heat. In addition to the heat from the body's metabolic results and the result of heat exposure from the work environment, heat strain on workers also influenced by individual factors. The extent to which an individual's body can tolerate heat exposure is determined by the condition of his body. Physiological changes will occur in the body of workers who exposed to heat. The objective of this study was to analyse factors related to heat strain such as acclimatization, water intake adequacy rate, and individual characteristics. The research was an observational analytic study and study design that used was cross-sectional. The population chosen as the research subject was workers who were exposed to heat. Purposively 57 construction workers were selected as subjects. To prove the relationship between acclimatization, water intake adequacy rate, and individual characteristics with heat strain, it used chi square statistical test. Physiological Strain Index (PSI) used to assess heat strain event on workers. The results of outdoor WBGT measurements at the study site showed that the average of WBGT outdoor was 31.11 o C. Heat strain with high index experienced by the majority of workers as much as 82.5%. Result of statistical analysis showed the significance of each variable was acclimatization (p<0.05), water intake adequacy rate (p<0.05), alcohol and drug consumption (p>0.05), health status (p>0.05), body mass index (p<0.05), age (p>0.05), and work period (p>0.05). This study showed that there was a significant relationship between heat strain with acclimatization, water intake adequacy rate and body mass index. The relationship is evidenced by the results of bivariate analysis. However, there was no association between consumption of alcohol or drugs, health status, work period, and age with heat strain.