The incidence of primary gastrointestinal lymphomas (PGILs) has been increasing. The clinical presentation and treatment of PGIL are distinct from those of nodular lymphomas. Symptoms include abdominal pain, abdominal mass, changes in bowel habits, obstruction, and bleeding. Less life-threatening gastrointestinal bleeding occurs after chemotherapy and few reports have focused on the bleeding of PGILs. We report a case of severe gastrointestinal bleeding caused by low-dose chemotherapy, which was dramatically improved by rituximab monotherapy treatment. The prevention and treatment of gastrointestinal bleeding in PGIL should be given much attention. The incidence of primary gastrointestinal lymphomas (PGILs) has been increased. The clinical presentation and treatment of PGIL are distinct from those of nodular lymphomas. Symptoms include abdominal pain, abdominal mass, changes in bowel habits, obstruction, and bleeding. Less life-threatening gastrointestinal bleeding occurs after chemotherapy and few reports have focused on the bleeding of PGILs. We report a case of severe gastrointestinal bleeding caused by low-dose chemotherapy, which was dramatically improved by rituximab monotherapy treatment. The prevention and treatment of gastrointestinal bleeding in PGIL should be given much attention