While recent studies have shown that wearable sensing technology has the potential to facilitate the evaluation of physical fatigue, the reliability and validity of such measurements during construction tasks have not been reported. Thus, the primary objective of the current study is to establish absolute and relative reliability of textile-based wearable sensors to monitor physical fatigue during bar bending and fixing construction tasks. The secondary objective is to establish correlations between physiological parameters and subjective fatigue scores or blood lactate levels in order to demonstrate the convergent validity. Physiological parameters such as heart rate, breathing rate, and skin temperature were evaluated using textile-based wearable sensors. The test-retest reliability (intra-class correlation coefficient - ICC) values of the measured resting and working heart rate (ICC = 0.73 and 0.85), breathing rate (ICC = 0.78 and 0.82), and skin temperature (ICC = 0.68 and 0.77) were moderate to good and good, respectively. There were moderate to excellent correlations (r-values ranging from 0.414 to 0.940) between physiological parameters and subjective fatigue scores, although there were no correlations between any physiological parameters and blood lactate levels. Both laboratory and field data substantiated that the wearable sensing system has the potential to be a reliable noninvasive device to monitor physical fatigue (especially among workers at risk of sustaining fatigue-related injury due to advanced age, poor health, or job nature. However, because the current study validated the system exclusively in bar benders, additional research is necessary to confirm the findings in other construction workers.