<p>Internet Gaming Disorder (IGD) is becoming more common in Indonesia as a result of increased internet usage, which is associated with psychological and physiological dysfunctions, including stress system dysregulation and cognitive impairment. This study aimed to analyze the relationship between IGD, salivary cortisol levels, and eye saccadic movements as neurocognitive indicators. This was an observational-analytic, cross-sectional study conducted among students of SMP Negeri 18 Medan. Over 217 students screened, 60 participants were recruited using consecutive sampling and divided into IGD (<i>n</i> = 30) and control (<i>n</i> = 30) groups based on the Game Addiction Scale (GAS). Salivary cortisol samples were collected in the morning under fasting conditions, while eye saccadic movement was assessed using the error rate parameter. Data were analyzed using Mann–Whitney, Chi-square, and point-biserial correlation tests. Salivary cortisol levels were significantly higher in the IGD group compared with controls (<i>p</i> = 0.015). The proportion of saccadic errors was also significantly higher in the IGD group (<i>p</i> = 0.004). In addition, a moderate positive correlation was found between salivary cortisol levels and saccadic error rates in the IGD group (<i>r</i> = 0.443; <i>p</i> = 0.014). These findings suggest increased physiological stress responses and impaired inhibitory control among adolescents with IGD. Salivary cortisol levels and eye saccadic movement may have potential as objective markers in the assessment of IGD.</p>