Objective To investigate interruptions occurring in the starting phase of hemodialysis and to provide reference for targeted interventions. Methods A direct observational study was conducted to identify the frequency, duration, sources and outcomes of interruptions occurring in the starting phase of hemodialysis. Results Thirty-four hemodialysis nurses were observed. In total, 2,611 interruptions occurred in 1,630 cases of hemodialysis, with the mean number of interruptions per observation being 1.6. The main source of interruptions was team staff (46.3%), followed by patients or family members (42.0%).The top three reasons for interruptions were double-check (45.5%), treatment-related conversation (22.0%), and non-treatment-related conversation (16.4%). Nurses′ actions or responses to the interruptions were engaging (57.2%), multi-tasking (20.2%), mediation (18.6%) and blocking (4.0%). A total of 2,354 interruptions (90.2%) caused negative outcomes, of which 43 were errors or potential adverse events (1.6%). Conclusion Interruption in the starting phase of hemodialysis is prevalent, multifaceted, complex and error prone. It is suggested to strengthen support and education for nurses, to ensure patient safety.