Incomplete left atrial appendage closure (LAAC) occurs in ∼30–40 % of cases following both surgical and percutaneous closure methods. Incomplete surgical LAAC may further be classified as incompletely surgically ligated LAA (ISLL) or LAA stump. ISLL is associated with a significantly increased risk of thrombus formation/thromboembolism. Moreover, this risk is highest in the absence of oral anticoagulation (OAC) and inversely correlates with the size of the ISLL neck. Not only routine screening for ISLL seems critical, but also long-term OAC should strongly be considered in this high-risk cohort. Alternatively, complete endocardial occlusion using a surrogate method may represent a reasonable option, particularly in those intolerant to long-term OAC therapy. Although thrombus formation/thromboembolic events have also been described in patients with incomplete LAAC following percutaneous occlusion, an association between the two remains less clear. However, given the rise and growing interest in percutaneous LAAC methods, additional research in this area is clearly warranted.