Nutritional status, workload, and sleep quality are key factors influencing job stress and employee productivity, especially in the physically and mentally demanding oil and gas industry. This study aimed to analyze how these three factors affect job stress and productivity, both directly and indirectly through stress as a mediating variable, at PT. Apexindo Balikpapan. Using a quantitative cross-sectional design, 100 respondents were selected via total sampling. Data collection involved questionnaires and physiological stress assessments using a Cocorometer (salivary alpha-amylase enzyme analysis). The variables included nutritional status, workload, sleep quality, subjective and objective stress, and productivity. Data were analyzed using Partial Least Square–Structural Equation Modeling (PLS–SEM). Results showed that nutritional status significantly affected stress (p = 0.006) and productivity (p= 0.006), both directly and indirectly (p=0.049). Workload had a significant positive effect on stress and a negative effect on productivity directly (p=0.012) and indirectly (p= 0.008; p=0.014). Sleep quality influenced subjective stress (p<0.05) and indirectly affected productivity (p=0.006), but had no significant effect on objective stress (p=0.426). It was concluded that the nutritional status, workload, and sleep quality significantly impact job stress and productivity, with stress acting as a key mediating factor.