Head constables Manmohan and Sanjiv found the red bag in a service lane on Pushta Road while they were on patrol duty.
The two constables took the bag in their possession after feeling suspicious about it, a senior police officer said.
"The bag contained Rs 12 lakh in the form of Rs 500 and Rs 2,000 notes. They displayed honesty and brought it to the notice of senior officers," the police officer said.
DCP (Shahdara) Nupur Prasad tweeted: "HC Manmohn & HC Sanjiv PS Gandhingar located a suspicious bag during patroling @ Pusta rd & found new curncy Rs 12L @DelhiPolice (sic)."