Purpose: We report a case in which oral sodium valproate through a percutaneous endoscopic gastrostomy (PEG) tube for palliative decompression drainage in inoperable ileus achieved an effective drug concentration and ameliorated delirium and extrapyramidal side effects. Case Report: The patient was a male in his seventies who suffered from bladder cancer. He underwent PEG because of paralytic ileus with cancerous peritonitis. He had been receiving continuous intravenous infusion of haloperidol for the management of delirium, but needed to discontinue treatment with this agent due to tremor, an extrapyramidal side effect of haloperidol. Oral sodium valproate was therefore administered through the PEG tube for palliative decompression drainage. Plasma valproate concentrations showed effective levels, and his irritability was relieved. A good combination of sodium valproate and quetiapine fumarate allowed successful reduction of and eventual withdrawal from haloperidol, and tremor then improved. Conclusion: We often encounter difficulty with symptom control for patients who cannot use oral medications. When medication by other routes is difficult, this case suggests that sodium valproate through a PEG tube for palliative decompression drainage may be useful as a last resort for improving delirium.