The police received a call at 5.25am from a person who had heard a woman call for help.
"It turned out that she had fallen from the third floor. The woman was sent to Haukeland university hospital, but we have been told that she is not seriously injured," police spokesman Preben Wallestad told the NTB news agency.
"We have detained a man who is in this thirties. He had access to the hotel room from where she fell, so we are investigating the incident further," Wallestad said.
The NRK network reported that witnesses saw the woman hanging out of the window clutching the curtain before she fell. Another witness said a man was seen running from the scene, information that the police declined to comment on.