The fixed-price-incentive contract has an estimated value of $2.4bn, along with additional options.
If all options are exercised, the cumulative value of the award would increase to $3.2bn.
Construction of LHA 9 will start in December this year and is slated to complete by September 2029.
The DoD noted that this period would extend until March 2031, if additional contract options are being exercised by the US Navy.
The company will carry out the associated work majorly at its site in Pascagoula, Mississippi, US.
HII Ingalls Shipbuilding president Kari Wilkinson said: “We understand how important this work is and consider it an honour to be given the opportunity to deliver this capability to the fleet.
“We value our partnership with the Navy and all of our critical supplier partners.”
The latest deal builds on the initially awarded contract to provide long-lead-time material, engineering and design support for the America-class landing helicopter assault (LHA) ship LHA 9.
So far, the company has handed over around 15 large-deck vessels to the US Navy, including the Tarawa-class ships LHA 1 to 5 and the Wasp-class ships LHD 1 to 8.
HII has also completed the delivery of two America-class ships USS America (LHA-6) and USS Tripoli (LHA-7), while construction for another vessel, Bougainville (LHA 8), is currently underway.