The MK 45 is a weapon for use against surface vessels and aircraft and can also be used against targets ashore in support of amphibious operations.
Under the award, BAE Systems will overhaul and upgrade two Mk 45 naval guns, bringing them to the 5-inch, 62-caliber Mk 45 Mod 4 configuration.
"This contract illustrates the Navy's commitment to equipping its ships with the most modern, reliable and precise naval gun systems in existence," said Mark Signorelli, vice president and general manager of Weapon Systems for BAE Systems.
"The cost-effective Mk 45 Mod 4 gun systems improve the accuracy and reliability sailors need to successfully support the Navy's broad spectrum of missions for its major combatants."
The upgrade will include strengthening of gun mounts, enhancement of its control system and addition of a modern touch-screen user interface.
Addition of a low maintenance gun shield will be included.
BAE Systems said work on the guns will be performed at facilities in Kentucky and Minnesota, and that the guns will be delivered to the Navy in 2014.