The fire erupted around midnight on Saturday, at a private clinic, according to the Moscow prosecutor's office.
According to the Moscow branch of the emergencies ministry, the fire occurred on the first floor of a three-story administrative building.
"Eight people were rescued, one person died," an emergencies ministry spokesperson told Sputnik.
The Moscow department of the Russian Investigative Committee said on social media that at least three people were hospitalized after the fire and one woman in her 40s died.
An investigation is underway.