A 37-year-old female presented with acute chlorpromazine and phenobarbital poisoning. Contrast enhanced abdominal CT on admission revealed a high density area at the gastric fundus and residual drugs were suspected. Activated charcoal and cathartics were administered following the gastric lavage under the intubation. As the plasma concentration of phenobarbital was high, urinary alkalinization and crystalloid infusion were carried out to reduce it. However, at 3 days after admission, the plasma concentration level had increased and the consciousness disturbance and respiratory depression continued. Abdominal CT was performed again and bezoars formation was suspected. Endoscopy was carried out to remove the bezoars. After the removal, the plasma concentration level significantly decreased. Her consciousness disturbance and respiratory depression also improved and high density area at the gastric fundus disappeared. Acute endoscopy is seldom advocated in cases of drug overdose. However, aggressive endoscopic removal should be considered in the case of acute poisoning of drugs with form bezoars.