To the best of our knowledge, there are no previous reports of a gastro-colic fistula (GCF) secondary to primary high-grade B-cell gastric lymphoma associated with acquired immunodeficiency syndrome (AIDS). Here, we report a 37-year-old man who presented with paroxysmal abdominal pain for 4 months, diarrhea for 15 days and weight loss of 4 kg. He had a history of human immunodeficiency virus (HIV) infection and was diagnosed with AIDS in 2013. The patient was diagnosed with a GCF secondary to primary high-grade B-cell gastric lymphoma by gastroscopy and histopathological examination. Two weeks after diagnosis, he died in another hospital. This is an uncommon case in which the GCF occurred secondary to malignant gastric lymphoma in a patient with AIDS. Supported by the literature, patients with HIV infection who complain of abdominal pain or a mass, severe diarrhea, and weight loss should be assessed for a GCF secondary to lymphoma because of its worse prognosis.