Task Force officers arrested the man in Waverley Park, off New Hall Lane, after a foot chase around city streets on Saturday (September 25).
He was detained and searched at the scene, with officers seizing what is believed to be bags of heroin and crack cocaine. The suspect's cash and mobile phone were also seized.
He was taken into custody for possession with intent to supply Class A drugs.
Following his arrest, officers searched the area around the park and also recovered the replica pistol.
Lancashire Police said the arrest was a result of anonymous tip-offs from the public who reported the man acting suspiciously.
A police spokesman said: "The male was located on Waverley Park and having made concerted attempts to escape was detained and transported to custody.
"As a result of the arrest a search was made of the vicinity and a realistic BB gun was located and seized.
"Enquiries are ongoing with the arrested male.
"It is with the continued support from the public that has assisted in this arrest and we thank those that came forward anonymously and would continue to encourage people to do so."
Are BB guns legal?
Most BB guns are legal in the UK, but it is considered an offence to carry those that resemble real firearms in a public place. Those caught wielding realistic BB guns in public can be arrested for possession of an imitation firearm, regardless of the power of the gun itself.