Thrombotic complications during and after extracorporeal membrane oxygenation (ECMO) are commonly observed clinically. The incidences of cannula-associated deep vein thrombosis (CaDVT) post-ECMO support have predominantly focused on Caucasian demographics. This study aims to determine the incidence and risk factors for CaDVT in Vietnamese patients following ECMO decannulation. The retrospective study from January 2019 to February 2020 observed ECMO weaning patients and screened for CaDVT using Doppler ultrasonography. Data were collected on patient demographics, ECMO parameters, and transfusion and coagulation profiles during ECMO support. Of the 82 patients successfully weaned ECMO, 89% were assessed for CaDVT. We observed a CaDVT incidence of 24.7%, and only one patient (5.6%) had a pulmonary embolism in the CaDVT group. Noteworthy is that the anticoagulation goals, transfusion during ECMO, and hospital mortality showed no significant difference between the CaDVT and non-CaDVT groups. The findings showed that the duration of ECMO support is a risk factor for CaDVT. The incidence of CaDVT following ECMO decannulation was 24.7%, and the diagnosis of CaDVT can be underestimated. Therefore, we suggest routine screening for CaDVT after cannula removal.