The Internet provides better access to knowledge, social interaction, and education for young adults, but excessive Internet use can lead to addiction. Catholic seminarians are another vulnerable group because they have daily and easy access to the Internet. This cross-sectional study aims to investigate the roles of social support and spiritual well-being in relation to Internet addiction among Indonesian seminarians. The study included 402 Indonesian seminarians enrolled in various Indonesian seminaries during the 2022-2023 academic year. Data collection was conducted through the Internet Addiction Test (IAT), the Multidimensional Scale of Perceived Social Support (MPSS), and the Spiritual Well-Being Scale (SWBS). The data were examined using descriptive statistics, the Pearson correlation coefficient, and stepwise regression analysis in SPSS version 23.0. The study found that seminarians had moderate levels of both spiritual well-being and perceived social support and that they had a mild level of Internet addiction. The Pearson correlation coefficient showed a significant negative correlation between perceived social support and Internet addiction (-0.217; p < .01). Similarly, spiritual well-being also revealed a negative correlation with Internet addiction (-0.341; p < .01). Stepwise multiple regression analysis revealed that existential well-being (& beta; = -0.344; p < .01) and friend support (& beta; = -0.105; p < .01) predict Internet addiction in Indonesian seminarians. These results suggest that encouraging seminarians to intensify their spiritual-based activities and seek support from friends in the seminary may help reduce their level of Internet addiction.