Jeetendra Kumar Jha, an Indian Civil Accounts Service officer, went missing from Dwarka on Monday after going for a walk, they said.
An unidentified body was found on the intervening night of December 11 and 12 on the railway tracks in Palam. It was identified as that of Jha after a wallet was found.
A purported suicide note was found from his pocket, in which he said that no one was responsible for his death, they added.
Jha, a 1998-batch officer, had left his home on Monday to drop off his children to their school bus and then returned home. He went out again a little later but left behind his phone, the police said.
It is suspected that Jha was upset over something as he was not going to office and was on medical leave from September 28, the police said.