Purpose: This study aimed to investigate factors affecting digital game addiction in secondary school students during the COVID-19 pandemic and the effects of digital game addiction on cardiovascular health behavior. Design and methods: This descriptive, correlational, and cross-sectional study was conducted with 619 secondary school students aged 10–14 years. Study data were analyzed using World Health Organization AnthroPlus and SPSS programs. Simple linear regression and multiple linear regression methods were used in the analysis process. Results: Findings showed that 43.6% of the students played digital games for more than two hours a day. Descriptive characteristics (gender, age, basal metabolic rate, educational status of parent, income status, etc.) and digital gaming habits of the students accounted for 37.0% of the variance in digital game addiction. Digital game addiction adversely affected cardiovascular health behavior and all its sub-dimensions. Conclusion: The first factor that predicted digital game addiction, in order of significance, was daily digital game playing time. Digital game addiction negatively affected the sedentary lifestyle sub-dimension of cardiovascular health behavior most. Digital game addiction may trigger an increase in the incidence of diseases such as diabetes, cancer, and especially cardiovascular diseases, at later ages. Practice implications: Nurses, schools, and parents have critical responsibilities in preventing digital game addiction. Results of this research will make a remarkable contribution to the development of preventive services by revealing risk factors for digital game addiction and the effects of digital game addiction on cardiovascular health behavior.