This is the second arrest in the case that had triggered widespread outrage with even Prime Minister Narendra Modi condemning the killing and directing the authorities to bring the culprits to book.
Earlier, a 19-year-old Delhi University student was arrested and a juvenile was arrested.
The 32-year-old victim, Ravinder Kumar, was beaten to death by nearly a dozen men on May 27, hours after he had objected to two men urinating in public outside the metro station in northwest Delhi.
The third accused, Mehul Deda, was arrested on June 4, said Deputy Commissioner of Police (Northwest) Milind Mahadeo Dumbere.
Deda was part of the group which had attacked Ravinder Kumar with towels and stones.
He had been on the run since the incident. He had been hiding in Rishikesh but returned to Delhi after he got to know that Kapasia and the juvenile had been nabbed.
He thought that the situation had eased now and decided to return, a police officer said.
Police said that they were looking for the other accused. The arrested duo will be questioned together to ascertain the identity of the other accused, police said.