Small bowel metastasis from primary lung cancer is rare. Once occurs, the metastasis may cause life-threatening complications, such as bowel perforation, obstruction and bleeding. We reported an 83-year old man who presented with small bowel perforation secondary to metastatic lung cancer after being treated with erlotinib for 2 weeks. We propose that the use of erlotinib may be associated with the small bowel perforation and precautions should be taken by clinicians in initiating erlotinib for primary lung cancer when there is bowel metastasis. Small bowel metastasis from primary lung cancer is rare. Once reported, the metastasis may cause life-threatening complications, such as bowel perforation, obstruction and bleeding. We reported an 83-year old man who presented with small bowel perforation secondary to metastatic lung cancer after being treated with erlotinib for 2 weeks. We propose that the use of erlotinib may be associated with the small bowel perforation and precautions should be taken by clinicians in initiating erlotinib for primary lung cancer when there is bowel metastasis.