The incident took place when constable Monu manning a traffic signal on the busy Preet Vihar Main road tried to stop three youth riding a motorcycle without helmets this evening.
They sped away from the spot.
After a few minutes, two of them returned wearing helmets and fired at the constable with a country made pistol but missed their target.
"A cartridge has been recovered from the spot while investigations are on," said a police official, "a case of attempt to murder has also been registered," he added.