Non-small cell lung cancer (NSCLC) is characterised by diffuse metastases, with common sites being the brain, liver, bones, and adrenal glands. Small bowel metastasis from NSCLC is a rare phenomenon, particularly in patients with an adenocarcinoma histology. We report the case of a 56-year-old lung adenocarcinoma patient with a duodenal metastasis diagnosed on FDG/PET-CT and confirmed on duodenal biopsy. Although initially asymptomatic, he subsequently presented with obstructive jaundice secondary to rapid local disease progression at the duodenal metastasis, requiring endoscopic intervention for biliary drainage. He was commenced on single agent pembrolizumab, with disease response on subsequent follow-up. This case highlights a rare case of gastrointestinal metastasis from NSCLC requiring endoscopic intervention due to rapid progression of the disease at the site of metastasis.