Abstract Immigration supervision is one of the strategic functions in maintaining state sovereignty by monitoring the presence and activities of foreign nationals within the territory of Indonesia. Following the Russia–Ukraine conflict, the increasing mobility of Russian and Ukrainian nationals to Bali has led to a higher potential for immigration violations, including the misuse of residence permits, overstaying, and engaging in employment inconsistent with the purpose of the granted visa. This study aims to analyze the effectiveness of immigration supervision of Russian and Ukrainian nationals following the Russia–Ukraine conflict within the jurisdiction of the Class I Immigration Office TPI Denpasar, as well as to examine the obstacles and efforts to improve the effectiveness of such supervision.This study employed an empirical legal research method using factual and statutory approaches. The data were collected through library research and interviews, and subsequently analyzed qualitatively using an inductive method.The results indicate that the effectiveness of immigration supervision is influenced by the implementation of administrative and field supervision, inter-agency coordination, the utilization of information technology, and community participation. Although immigration supervision has been strengthened through joint operations and coordination within the Foreigner Supervision Team (TIMPORA), its effectiveness continues to face several challenges, including limited human resources, the high mobility of foreign nationals, the misuse of residence permits, suboptimal inter-agency coordination, and low public participation. Efforts to improve the effectiveness of immigration supervision include strengthening the capacity of immigration officers, optimizing the use of information technology, enhancing TIMPORA coordination, implementing intelligence-based supervision, and increasing public awareness through continuous outreach to communities and business operators. Keywords: Effectiveness, Immigration Supervision, Russian and Ukrainian Nationals, Residence Permit.