The killings since June 28 in Lahore spread fear and panic among the 200,000 homeless people in Pakistan’s second-largest city.
A senior police officer told Reuters that the suspect, who he identified only as Aamir, was arrested on Monday night and had confessed to the killings.
He said the 24-year-old man appeared mentally deranged.
The victims of the killing spree were all homeless men, including labourers, beggars and drug addicts, and were bludgeoned to death with bricks while sleeping.
“We caught him last night while he was trying to escape after hitting a homeless man, who was sleeping, with a brick,” Superintendent of Police Dr Usman Anwar said of the suspect.
“He has a history of violence and is the only brother of five sisters who claim he is also frequently violent with them and is a psychopath,” Anwar said.
Last year, 15 homeless people were killed in Lahore by being bludgeoned with bricks before police arrested three men.
One suspect confessed to killing 11 people and was sentenced to death. The other two were released due to lack of evidence.
Usman said Aamir had been asked why he used bricks to kill his victims and had replied: “When such free weapons are available on the road, why spend money?” Usman said the man Aamir had attacked when he was caught survived.
Pakistan’s worst modern-day serial killer was Javed Iqbal, who in 1999 confessed to murdering 100 children and dissolving their remains in acid to avenge having been beaten by police.