BACKGROUND: Extracorporeal membrane oxygenation (ECMO) as rescue therapy for cardiogenic shock (CS) is highly dependent on timeliness and medical resources. OBJECTIVES: Aimed to assess ECMO management and outcomes in adult patients with CS in terms of on- and after-hour ECMO initiation from a national ECMO registry. METHODS: Adult patients diagnosed with CS and those who received ECMO were enrolled in the study. The population was divided into the work-hours and the after-hours group based on the time of ECMO initiation. In-hospital mortality and ECMO management were compared between them. Electronic data in this research were provided by Chinese Society of Extracorporeal Life Support. RESULTS: In a cohort of 1862 patients, 552 (29.6%) received ECMO during work-hours, whereas 1310 (70.4%) received ECMO during after-hours. After-hour ECMO had more patients with elective cardiac procedures (35.1% vs. 26.3%, p <
0.001) and higher severity (p <
0.001), with more patients with Society for Cardiovascular Angiography and Interventions shock stage D (29.6% vs. 24.5), E (60.0% vs. 51.8%), and fewer B (3.6% vs. 13.2%) and C (6.8% vs. 10.5%). A high proportion underwent intra-aortic balloon pump (IABP) implantation before ECMO (28.4% vs. 23.0%, p = 0.016) and mechanical ventilation (92.1% vs. 87.0%, p <
0.001) during after-hours. The in-hospital mortality in patients with after-hour ECMO initiation was higher than that in patients with work-hour ECMO initiation (51.8% vs. 45.3%, p = 0.011). CONCLUSION: In this cohort, 70% were initiated during after-hours and showed higher in-hospital mortality than patients with work-hour ECMO initiation. After-hour ECMO initiation should be a concern for ECMO programs.