Officers seized three drones yesterday (September 7) and issued a warning.
There is a no-fly zone in place until midnight tonight (September 8).
A police spokesperson said: “People of Preston, you are doing our city proud at Radio 2 In The Park Festival in Moor Park by showing the nation what a fun-loving bunch we are.
“Unfortunately a small number of people have ignored the no-fly zone and we have had to seize three drones.
“Just a reminder that the airspace restriction remains in place between 12pm and 11.59pm today and tomorrow. They are there to keep everyone attending the festival safe.”