Each of the copters fired one Hellfire guided missile at a shooting range in the waters off the western coastal city of Gunsan, according to the Army.
They flew 60 kilometers before firing and all exactly hit the targets on the sea, the Army said.
The Army introduced 36 Apache helicopters produced by Boeing in May last year and deployed them in January.
The Hellfire missiles were launched from different distances and in different manners so the pilots can better familiarize themselves with the missile, it also noted.
Four more Apache helicopters also joined the live-fire exercise as command and back-up planes.
"True to its name, the Hellfire is a strong guided missile that can completely destroy enemy targets. This is the first time the South Korean military has carried out a live-fire exercise with the missiles," the Army said. The exercise is designed to "bring the Army's air fighting power up by one level after introducing the Apache helicopters in May last year."
With a range of 8 km, the Hellfire has been used by the US military in Iraq and Afghanistan. One Apache chopper can carry up to 16 Hellfire missiles.
The South Korean Army's Apache unit, with its equipment and personnel, is capable of destroying 570 enemy tanks, according to the Army.
"The adoption of the Hellfire missile has equipped the military with the ability to destroy various enemy targets from a longer distance and has increased the chances of our attack helicopters' survival and our destructiveness against enemy tanks," the Army said.
The US choppers would be mobilized to attack North Korean tanks and air-cushion vehicles in the event of armed conflict. They will also be among the first to be sent if North Korea launches a surprise landing on South Korea's frontline islands between the two Koreas.
The United States Forces Korea also operates 48 Apache helicopters. (Yonhap)