The incident was reported around 11.30 PM yesterday, they said.
The duo was at their friend's birthday party last night in Hauz Rani area near Select Citywalk Mall when the two persons were attacked, the police said.
While Aman alias Karan and his friend Amit (21) were waiting for their friends to come, five men armed with knives and rods attacked them.
Aman was stabbed multiple times by the accused and when Amit tried to intervene, he was stabbed too.
The accused also attacked the victims with iron rods. The duo was rushed to a hospital where Aman was declared brought dead. Amit is undergoing treatment, the police said.
In his statement, Amit said they had gone to a friend's room in Hauz Rani to celebrate the birthday of their friend Gaurav.
Police suspect that it was a planned attack and could be the fallout of a dispute between the victims and the accused.
The five accused have been identified but no arrests have been made so far.
Raids are being conducted to arest the accused, police said.
In a similar incident, a 23-year-old man, Prahlad, was stabbed to death allegedly by his two friends following an argument in northwest Delhi's Bhalswa Dairy last night.
The police said they have identified the accused and will arrest them soon.