Strongyloidiasis, a chronic helminth infection caused by the parasitic nematode Strongyloides stercoralis, has various clinical manifestations. Although rare, duodenal obstructions and venous thromboembolism are possible complications of strongyloidiasis.This paper presents the case of a 47-year-old Vietnamese male with a history of right lower limb edema, anorexia, nausea, vomiting, diarrhea, and abdominal discomfort lasting for four months. Venous Doppler ultrasound detected a thrombus in the right femoral vein, while an abdominal CT scan revealed a mass lesion suggestive of a lower bile duct tumor. Esophageogastroduodenoscopy showed a friable duodenal cap mucosa with multiple ulcers and edematous mucosa of the second part of the duodenum that caused a partial lumen obstruction. The final histological examination of the biopsy specimen revealed chronic duodenitis with larvae consistent with Strongyloides stercoralis. The patient was treated with Ivermectin for two weeks and anticoagulation therapy for three months. After treatment and a six-month follow-up, the patient's gastrointestinal symptoms and leg swelling resolved completely. This is the first documented case of a patient in Vietnam with strongyloidiasis who presented with venous thromboembolism and duodenal obstruction. (Korean J Gastroenterol 2023;81:270-275)