Cannula-associated deep vein thrombosis (CaDVT) following decannulation from extracorporeal life support (ECLS) is a commonly reported complication with several associated risk factors. This study investigated the incidence and risk factors of CaDVT after ECLS decannulation from a nationwide registry. We analyzed consecutive patients who were successfully decannulated from ECLS and screened for CaDVT from two medical-surgical intensive care units (ICU) in Kuwait between 2016 and 2023. The incidence of CaDVT was assessed and correlated with risk factors such as baseline characteristics, ECLS mode and duration, and cannula sizes. Length of stay (LOS) in the ICU, along with ICU and in-hospital mortality were reported. Of 403 patients supported with ECLS, 144 underwent postdecannulation ultrasound. Cannula-associated deep vein thrombosis occurred in 94 (65%) patients. Venovenous ECLS (V-V ECLS) was the only independent risk factor associated with post-ECLS CaDVT (odds ratio [OR]: 4.78; 95% confidence interval [CI]: 1.18–19.4). Length of stay in the ICU and mortality were similar between patients with and without CaDVT. Cannula-associated deep vein thrombosis is a frequent complication of ECLS, occurring in more than half of patients. The use of V-V ECLS appears to be an independent risk factor for the development of post-ECLS CaDVT. Further efforts are needed to develop formal recommendations for screening and managing CaDVT post-ECLS.