Safe sedation doses for performing minor procedures such as bronchoscopy, endoscopy, and tooth extraction for beluga whales (Delphinapterus leucas) require elucidation. This study aimed to provide suggestions for determining appropriate midazolam and butorphanol doses to adequately sedate beluga whales to complete procedures and minimize the risk of side effects. We administered midazolam and butorphanol to six captive beluga whales (9-44 years old). Topical lidocaine anesthesia was administered during bronchoscopy. The sedation doses for the beluga whales varied from 0.020 to 0.122 mg/kg for midazolam and from 0.020 to 0.061 mg/kg for butorphanol. In beluga whales, optimal midazolam and butorphanol doses were lowest in old whales. These findings contribute to knowledge regarding appropriate sedation and prevention of overdose accidents during minor procedures in beluga whales.