Inverted left atrial appendage (iLAA) is an infrequent complication following cardiac surgery, seen both in children and adults. Following a recent encounter, this review article is aimed to remind the reader about its occurrence, clinical manifestations, differential diagnoses, and management options. A 3-month-old baby underwent successful surgical repair of a large ventricular septal defect. Intraoperative epicardial echocardiogram at the end of the case demonstrated an unexpected left atrial mass, raising suspicion of a thrombus adjacent to the mitral valve. Urgent re-establishment of cardiopulmonary bypass and exploration of the left atrium did not reveal a thrombus, but this was subsequently identified as an iLAA. This completely resolved after manual external reduction of the appendage. Published literature is confined to case reports only, with most cases observed post-operatively, but some occurring spontaneously. Awareness of this unusual manifestation is particularly important in the intraoperative period as it can usually be addressed without the need for further cardiopulmonary bypass.