A Central Industrial Security Force official said the incident was reported around 12:20 pm at the Adarsh Nagar metro station.
He said an on-duty force personnel detected a pistol-like object in a bag being screened at the X-ray machine.
The bag belonged to a man identified as Bhupendra K (19) and his associate G Singh (32), residents of Firozabad in Uttar Pradesh.
A country-made pistol and Rs 1,59,898 in cash was seized from the bag, the official said.
Carrying arms and ammunition in the Delhi Metro is banned under law.