According to the Extracorporeal Life Support Organization (ELSO) guidelines, pre-assembled and already primed extracorporeal membrane oxygenation (ECMO) systems can be safely stored for up to 30 days under specific conditions. This study gives a detailed overview of existing pre-assembly practices. An anonymous online survey was conducted among chief perfusionists at German ECMO centers. Forty-four of a total of 83 ECMO centers (53%) completed the survey. Thirty-three percent do not preassemble ECMO systems. Seventy-seven percent (n = 34) reported having preassembled ECMO systems readily available (30% dry preassembly/20% wet preassembly/27% wet preassembly with circulation). Half of the participating centers (50%) reported having a standard operating procedure (SOP) and the majority (57%) of chief perfusionists expressed a need for an evidence-based SOP. A maximum storage time for wet preassembled ECMO systems is established in 88% of departments. On average, wet preassembled systems are discarded after 20 days, which is below the ELSO’s safe limit of 30 days. Overall, this survey reveals a heterogeneous approach regarding the practice of provisioning preassembled ECMO systems. The demand for an evidence-based SOP for the preassembly and storing of ECMO systems becomes evident, necessitating the determination of hygienic standards, regular training, and a reliable maximum storage period.