Pseudoachalasia, also known as secondary achalasia, is a rare clinical condition mimicking idiopathic achalasia but unrelated to primary loss of nitrergic innervation. It has mostly been attributed to malignancy infiltrating the oesophageal wall, but several other benign underlying pathologies have been reported. Because of similar manometric appearance, high-resolution manometry (HRM) of the oesophagus alone cannot distinguish between idiopathic achalasia and pseudoachalasia. Misdiagnosis can result in ineffective treatment by dilatation or even more invasive therapy. This is the first case-report of pseudoachalasia secondary to oesophageal deviation resulting from mediastinal shift and left atrial enlargement following prior left lower lobectomy. HRM, the gold standard for the diagnosis of achalasia, confirmed the incomplete relaxation of the lower oesophageal sphincter (LES) in absence of normal oesophageal peristalsis. However, additional workup with CAT scan and cardiac ultrasound identified an anatomical shift by the extrinsic mass effect resulting from the atrial enlargement, but without contrast retention at the LES.