Accused Arjun Mahto of Bihar was arrested in 2013 but escaped from state police custody in July 2014 and shifted to Delhi.
"He was arrested on Tuesday evening when he had came to procure weapons from the Kiran garden area," Deputy Commissioner of Police (south west) Surender Kumar told reporters.
"He revealed his role in the brutal gang rape and murder of the girl in Bihar's Sitamarhi district," the officer said.
He was involved in cases of snatching and robbery in Delhi," the DCP said.
Kumar said Mahto was procuring weapons as he planned to go back to Bihar and form his own gang. A stolen motorcycle has been seized from his possession.
