The contract for the Mod 0 guns, to be delivered in 2014, is worth more than $20 million, BAE Systems said.
In addition to the guns, BAE Systems will provide engineering support.
"We are proud to equip the sailors that defend our country's coastline with the best in naval gun technology," said Mark Signorelli, vice president and general manager of Weapon Systems for BAE Systems.
"The versatility of the Mk 110 provides our armed services with the ability to take on today's expanding range of surface, airborne and shore-based threats."
One gun is destined for the Coast Guard's fifth National Security Cutter, while another is for the Navy's training facility in Dam Neck, Va.
The gun system can fire up to 220 rounds per minute at a distance of as much as 10.5 miles. BAE said the guns are fully automatic and able to immediately switch between ammunition types.
BAE Systems has far produced 19 of the compact-sized Mk 110 guns, which are controlled by a fire-control computer but can also be manually operated.