Extracorporeal membrane oxygenation (ECMO) exposes patients to multiple radiologic studies. We hypothesized ECMO patients endure radiation exposure in excess of the International Commission of Radiological Protection (ICRP) recommendations of cumulative effective dose (CED, >20 mSv and 5-year cumulative limit of CED >100 mSv). We conducted a retrospective observational study in an academic medical center between January 2016 and December 2018 involving adult admissions (N = 306) on ECMO. Ionizing radiation was calculated from reference values to determine CED. Approximately 9.4% (N = 29) patients accrued CED >50 mSv and 4.5% (N = 14) accrued CED >100 mSv during ECMO. Over the entire hospitalization, 28% (N = 85) accrued >50 mSv and 14.7% (N = 45) accrued CED >100 mSv. Median CED during ECMO was 2.3 mSv (IQR, –0.82 to 8.1 mSv), and the entire hospitalization was 17.4 mSv (IQR, –4.5 to 56.6 mSv). Thirteen percent of the median CED accrued during hospitalization could be attributed to ECMO. Longer hospitalization was associated with a higher CED (50 days [IQR, –25 to 76 days] in CED >50 vs. 19 days [IQR, –10 to 32 days] in CED <50). Computer tomography (CT) scans and interventional radiology (IR) procedures contributed to 43.8% and 44.86%, respectively, of CED accrued on ECMO and 52.2% and 37.1% of CED accumulated during the whole hospitalization. Guidelines aimed at mitigating radiation exposure are urgently needed.