Smartphone usage in schools has become a primary concern within the Cambodian educational sector. While numerous international studies have highlighted the impact of smartphones on students' academic performance and well-being, scientific research within the Cambodian context remains limited. This study aims to investigate the influence of smartphone addiction proneness on academic achievement, psychological stress, and physical health among high school students in Cambodia. Employing a quantitative research methodology, data were collected through convenience and snowball sampling techniques. The study involved a total of 129 participants from a province in Cambodia. Data analysis was conducted using descriptive statistics, correlation analysis, and simple regression analysis via SPSS version 27. The correlation results indicate that smartphone addiction proneness has a statistically significant positive relationship with psychological stress and physical health issues; however, no significant correlation was found with academic achievement. Furthermore, regression analysis confirmed that smartphone addiction proneness is a significant predictor of increased psychological stress (β = 0.296) and physical health problems—such as eye strain, sleep disturbance, and memory decline (β = 0.182). Notably, it was not a significant factor affecting academic performance. These findings provide a foundation for parents and schools to develop technology management strategies to enhance student well-being.