We report here two cases of advanced colorectal cancer which received chemotherapy, in which partial splenic embolization (PSE) had been effective for controlling splenomegaly and thrombocytopenia. Case 1: A 50-year-old man presented with bloody urine and bloody stool. Computed tomography (CT) showed rectosigmoid cancer with urinary bladder invasion. He underwent colostomy and received chemotherapy. After 3 courses of FOLFOX and 6 courses of bevacizumab/FOLFOX, he suffered from thrombocytopenia with splenomegaly, which led to discontinuation of the therapy. PSE improved thrombocyte counts and enabled him to resume therapy. Case 2: A 72-year-old man presented with bloody stool. Endoscopy and CT showed an advanced rectosigmoid cancer with multiple liver metastases. He underwent low anterior resection and received chemotherapy with FOLFOX and FOLFIRI, together with bevacizumab. After 13 courses of chemotherapy, he also suffered from splenomegaly and thrombocytopenia. PSE produced an increase in thrombocyte count and allowed for a restart of chemotherapy. Oxaliplatin-based chemotherapy may possibly produce hepatic sinusoidal dilation and induce splenomegaly owing to portal hypertension. PSE seemed to be useful for treating thrombocytopenia with splenomagaly, and allowed continuation of the chemotherapy.