Police arrested the boy in Haslam Park at 1.45am this morning (Wednesday, May 29) after a stop and search revealed he had been carrying a large knife concealed in his tracksuit pants.
Officers said they had visited the park to provide a more visible presence after a number of reports concerning anti-social behaviour.
During their patrols, officers spotted two males "acting suspiciously" near Bristow Avenue.
Using their stop and search powers, the officers detained them and recovered a large kitchen knife from the youngest suspect.
The illegal knife was seized and a 15-year-old boy has been arrested and taken into custody.
A spokesman for Preston Police said: "We are aware of concerns which have been raised recently on our Facebook in relation to ASB which has been occurring around Haslam Park, Ashton on Ribble, Preston.
"Throughout the night we’ve been providing a visible presence in the area, stopping and speaking with numerous people.
"At around 1.45am officers have spotted two males acting suspiciously in the vicinity of the park.
"Officers have detained both males for a search for weapons and sadly, once again, a very large knife was located in the waist band of a 15-year-old boy.
"Clearly someone carrying such a weapon had only one intention and by taking this off our streets we’ve hopefully prevented serious if not fatal injuries tonight."
"The 15-year-old male was arrested and has spent the rest of the night in the cells!"