Responding police officers closed the park to pedestrians for hours to search for the weapon until it was located.
Authorities say the injured man was found on the southwest corner of the park just after 5:15 a.m.
He had sustained a gunshot wound to his leg and was taken to Bellevue Hospital with a non life-threatening injury.
Investigators say an unspent round was discovered in his pocket, and police immediately suspected the wound was self-inflicted.
Surveillance video later recovered by police reportedly showed the man accidentally shooting himself while sitting on a park bench.
The man is seen throwing the gun away as he walked to the intersection of Washington Square South and MacDougal Street, where he was discovered following a 911 call.
Police officers canvassed the park until they found the gun.
The man is said to have an extensive criminal history, including arrests for drug dealing and possession.
NewsCopter 7 was above the crime scene Friday morning: