We report two cases of malignant afferent loop obstruction following pancreaticoduodenectomy (PD). Case 1. A 70-year-old woman, who had undergone PD for pancreatic cancer, was referred to our hospital because of fever, jaundice, and abdominal pain. Ultrasonography and abdominal computed tomography demonstrated dilatation of a small bowel loop in the right upper quadrant. Laparotomy confirmed the diagnosis of local recurrent tumor causing occlusion of the afferent limb, and Roux-en-Y bypass was performed. Case 2. A 72-year-old man, who had undergone PD for cancer of the major papilla, was hospitalized with a high-grade fever and epigastric pain. Ultrasonography and abdominal computed tomography revealed a dilated afferent loop and multiple masses in liver. At laparotomy, widespread carcinomatosis was found to have caused afferent loop obstruction, and surgical bypass was performed. In conclusion, the surgical bypass seems to be an effective palliative treatment for afferent loop syndrome after PD.