Objective: We describe a case of lung cancer complicated with esophageal achalasia (EA), which was successfully treated with endoscopic pneumatic dilation (EPD). Case: A 66-year-old woman was admitted to our hospital because of frequent episodes of emesis and dysphagia after receiving an escalating dose of sustained release oxycodone (SRO) for cancer-related multifactorial back pain. She had been diagnosed with EA and treated with EPD at the age of 50. Her symptoms were refractory to the conventional anti-emetic agents such as prochlorperazine and metoclopramide. Computed tomography imaging showed marked dilatation of the esophagus with food residue. We diagnosed EA based on the presence of rosette-like esophageal folds on endoscopy and narrowing of the esophagogastric junction on esophagography, and subsequently performed EPD, which alleviated the symptoms. Discussion: The effects of opioids on esophageal motility have not been elucidated thus far. Recent studies using high-resolution manometry reported that long-term use of opioids was associated with esophageal dysmotility similar to that observed in EA. Although we have no evidence to directly demonstrate the causal relationship between the use of SRO and anti-emetic agents and EA, we speculate that our patient’s symptoms might be associated not only with SRO-related emesis during the gradual worsening of EA, but also partly with the SRO-induced esophageal dysmotility and the constrictive effect of dopamine D₂ receptor antagonists on the lower esophageal sphincter. Care must be taken to avoid drug-induced esophageal motor dysfunction, which might lead to deteriorate EA.