Purpose: This study investigated the factors influencing smartphone overdependence in university students using an ecological model and descriptive research. Methods: Data were collected from 482 students at 13 universities in the six regions in South Korea from October 20, 2020, to March 25, 2021. Data analysis involved descriptive statistics, the chi-square test, the independent samples t-test, analysis of variance, and hierarchical multiple regression. Results: The significant ecological factors influencing smartphone overdependence included self-awareness of smartphone overdependence (beta=.33, p<.001), autonomy (beta=-.25, p<.001), average daily smart- phone usage time (beta=.18, p<.001), gender (beta=.15, p=.001), college year (beta=.15, p=.020), forming relationships with others as a motivation for smartphone use (beta=-.15, p=.008), friend support (beta=.14, p=.006), and age (beta=-.12, p=.047). The model explained 34.9% of the variance. Conclusion: The study emphasized the role of personal and interpersonal factors, in smartphone overdependence among university students. Tailored intervention strategies are necessary to address smart- phone overdependence, considering the unique characteristics of students'environments. A significant aspect of this study is that it provides an explanation of the multidimensional factors contributing to smartphone overdependence among university students, including intrapersonal, interpersonal, and environmental influences.