Officials said the incident happened at the Seelampur Metro station at about 6:00 PM.
CISF officials on duty detected a .315 bore country-made pistol and two rounds of ammunition in a bag during X-ray check.
The CISF men intercepted the two men, from Uttar Pradesh's Badayun district, who were carrying the pistol and live cartridges.
"Arms and ammunition are not allowed inside the Delhi Metro as per law. The duo were asked why these items were kept in their bag and upon getting no satisfactory answer, they were handed over to Delhi Police," a senior official said.