This quantitative-correlational study aimed to examine the relationship between online game addiction and mental well-being of high school students from Angeles City, in the Philippines, during the COVID-19 pandemic. To obtain data from the respondents, the Internet Gaming Disorder Scale--Short-Form and Depression, Anxiety, and Stress Scale (DASS-21) were utilised. After obtaining data from purposively selected 162 high-school students, it was observed that there was a positive and significant relationship between online game addiction and mental well-being. The study highlighted that individuals who are highly dependent on online games are more likely to experience higher levels of depression, anxiety and stress. Based on the findings, implications for theory and practice, particularly in learning and development, are presented, along with recommendations for schools, teachers, students, and future research directions.