An Uber driver is being questioned over the alleged sexual assault of a 22-year-old woman in Brisbane's north overnight.

According to police, the woman and three friends ordered an Uber in Fortitude Valley early Wednesday morning, with the other three people dropped off first.

An Uber driver has been arrested after an alleged sexual assault. Credit:Dominic Lorrimer

The 49-year-old driver allegedly sexually assaulted the woman as he dropped her off, about 12.20am, a police spokeswoman said.

She said there was no mention of the alleged victim needing to be hospitalised.

After initially saying the man had been taken into custody at the North Brisbane Criminal Investigation Branch in Carseldine, police said the man was assisting police with investigations at an address but had not been arrested.

NOTE: This story has been updated after police advised the man had not been arrested.