Transdiaphragmatic intercostal hernia (TDIH) is a rare condition involving simultaneous disruption of the diaphragm and intercostal muscles, allowing abdominal organs to herniate into the chest wall. It is usually traumatic and spontaneous cases are uncommon and can be easily overlooked. We report the case of a man in his late 60s with six years of progressive right chest wall swelling and recent vomiting and breathlessness. Initial imaging was misinterpreted as pleural effusion, but a computed tomography confirmed a five cm diaphragmatic defect with bowel herniation through the 7th –8th intercostal space. Prompt recognition is vital, as delayed diagnosis may lead to bowel obstruction, strangulation, and life -threatening complications