Those arrested have been identified as Bharat and Sandeep who attacked one Harish Pandey for resisting robbery attempt last month.
They were arrested yesterday following a tip off that they would be coming towards Nangloi underpass.
A trap was laid and they were arrested, a police official said.
"On August 24, Bharat along with Sandeep tried to rob Pandey in Mangolpuri area. When victim objected, Bharat stabbed him to death and the duo later fled the spot," said a police official.
Police has recovered the stolen mobile phone from them, the officials added.