Photos posted on social media showed people crowding around the boards to find out the latest on their flights.
Staff could also be seen rubbing out information as it changed to update it.
Gatwick Airport tweeted: “We are sorry, but due to an IT issue our flight information is not displaying correctly. Please use the temporary flight boards in the departure lounges or listen for airline flight announcements.
“We are expecting to resolve the issue soon and apologise for the inconvenience.”
There was frustration among some passengers who described walking to wrong gates or having their flights delayed.
A user by the name of @helenwalsh tweeted: “Absolute carnage @Gatwick_Airport with no boards working and no staff with gate info.”