On 2 August 1964, North Vietnamese torpedo boats attacked destroyer Maddox in the Gulf of Tonkin incident.
Valley Forge then spent 57 days at sea off the Vietnamese coast in readiness to land its Marines if required.

Returning to Long Beach on 5 November, Valley Forge made two round-trip voyages to Okinawa carrying marines and aircraft before commencing a WestPac deployment in the South China Sea in late 1965.
With a Marine landing force embarked and flying the flag of Commander, Amphibious Squadron 3, Valley Forge conducted intensive training exercises in the Philippines while preparing for service in Vietnam.

In mid-November, the amphibious assault ship stood by in reserve during Operation Blue Marlin and then airlifted its marines ashore for Operation Dagger Thrust and Operation Harvest Moon before spending the Christmas season in Okinawa.
After embarking a fresh Marine battalion and a medium transport helicopter squadron, it sailed for South Vietnam on 3 January 1966.
Following pauses at Subic Bay and Chu Lai, Valley Forge arrived off the Vietnamese coast on 27 January and, two days later, launched its landing forces to take part in Operation Double Eagle.
Remaining on station off the coast, the ship provided logistic and medical support with inbound helicopters supplying the men ashore and outbound helicopters evacuating casualties for medical treatment back on the ship.
Reembarking its landing team on 17 February, Valley Forge proceeded northward, while its Marines rested.
The second phase of "Double Eagle" commenced two days later, and the ship's Marines again went ashore via helicopter to attack enemy concentrations.
By 26 February, the operation had drawn to a close, and Valley Forge reembarked its Marines and sailed for Subic Bay.

Following a round trip to Đà Nẵng, the carrier steamed back to the west coast for an overhaul and local training along the California coast before again deploying to WestPac.
Upon its return to Vietnamese waters, the ship took part in operations off Đà Nẵng before it again returned to the United States at the end of the year 1966.

After undergoing a major overhaul and conducting training off the west coast, Valley Forge returned to the Far East again in November 1967 and took part in Operation Fortress Ridge, launched on 21 December.
Air-landing its troops at a point just south of the Vietnamese Demilitarized Zone (DMZ), the ship provided continual supply and medical evacuation (Medevac) services for this "search and destroy" operation aimed at eliminating People's Army of Vietnam (PAVN) units which threatened American and South Vietnamese troops.
The completion of this operation on the day before Christmas 1967 did not mark the end of Valley Forge's operations for this year, however, as it was again in action during Operation Badger Tooth, near Quảng Trị in northern South Vietnam.

Upkeep at Đà Nẵng preceded its deployment to its new station off Đồng Hới, where it provided her necessary resupply and MedEvac support for Allied troops operating against PAVN forces.
Operation Badger Catch, commencing on 23 January 1968 and extending through 18 February, supported the Cửa Việt Base, at the mouth of the Thạch Hãn River south of the DMZ, before the ship set course for Subic Bay and much-needed maintenance.

Subsequently returning to Vietnam, Valley Forge operated as "Helo Haven" for Marine helicopter units whose shore bases had come under attack by PAVN ground and artillery fire.
During Operation Badger Catch II, from 6 March – 14 April, Marine helicopters landed on board the carrier while their land bases were being cleared of PAVN troops.
Following a routine refit at Subic Bay, the ship took part in Operation Badger Catch III from 28 April – 3 June.
It then moved to Đà Nẵng and prepared for Operation Swift Saber which took place from 7–14 June.
Landing Exercise Hilltop XX occupied the ship early in July.
Then Valley Forge transferred its Marines and helicopters to Tripoli and headed home via Hong Kong, Okinawa, and Pearl Harbor.
She reached Long Beach on 3 August.

Following five months on
On 2 August 1964, North Vietnamese torpedo boats attacked destroyer Maddox in the Gulf of Tonkin incident. Valley Forge then spent 57 days at sea off the Vietnamese coast in readiness to land its Marines if required.
Returning to Long Beach on 5 November, Valley Forge made two round-trip voyages to Okinawa carrying marines and aircraft before commencing a WestPac deployment in the South China Sea in late 1965. With a Marine landing force embarked and flying the flag of Commander, Amphibious Squadron 3, Valley Forge conducted intensive training exercises in the Philippines while preparing for service in Vietnam.
In mid-November, the amphibious assault ship stood by in reserve during Operation Blue Marlin and then airlifted its marines ashore for Operation Dagger Thrust and Operation Harvest Moon before spending the Christmas season in Okinawa. After embarking a fresh Marine battalion and a medium transport helicopter squadron, it sailed for South Vietnam on 3 January 1966. Following pauses at Subic Bay and Chu Lai, Valley Forge arrived off the Vietnamese coast on 27 January and, two days later, launched its landing forces to take part in Operation Double Eagle. Remaining on station off the coast, the ship provided logistic and medical support with inbound helicopters supplying the men ashore and outbound helicopters evacuating casualties for medical treatment back on the ship. Reembarking its landing team on 17 February, Valley Forge proceeded northward, while its Marines rested. The second phase of "Double Eagle" commenced two days later, and the ship's Marines again went ashore via helicopter to attack enemy concentrations. By 26 February, the operation had drawn to a close, and Valley Forge reembarked its Marines and sailed for Subic Bay. 
Following a round trip to Đà Nẵng, the carrier steamed back to the west coast for an overhaul and local training along the California coast before again deploying to WestPac. Upon its return to Vietnamese waters, the ship took part in operations off Đà Nẵng before it again returned to the United States at the end of the year 1966.
After undergoing a major overhaul and conducting training off the west coast, Valley Forge returned to the Far East again in November 1967 and took part in Operation Fortress Ridge, launched on 21 December. Air-landing its troops at a point just south of the Vietnamese Demilitarized Zone (DMZ), the ship provided continual supply and medical evacuation (Medevac) services for this "search and destroy" operation aimed at eliminating People's Army of Vietnam (PAVN) units which threatened American and South Vietnamese troops. The completion of this operation on the day before Christmas 1967 did not mark the end of Valley Forge's operations for this year, however, as it was again in action during Operation Badger Tooth, near Quảng Trị in northern South Vietnam.
Upkeep at Đà Nẵng preceded its deployment to its new station off Đồng Hới, where it provided her necessary resupply and MedEvac support for Allied troops operating against PAVN forces. Operation Badger Catch, commencing on 23 January 1968 and extending through 18 February, supported the Cửa Việt Base, at the mouth of the Thạch Hãn River south of the DMZ, before the ship set course for Subic Bay and much-needed maintenance.
Subsequently returning to Vietnam, Valley Forge operated as "Helo Haven" for Marine helicopter units whose shore bases had come under attack by PAVN ground and artillery fire. During Operation Badger Catch II, from 6 March – 14 April, Marine helicopters landed on board the carrier while their land bases were being cleared of PAVN troops. Following a routine refit at Subic Bay, the ship took part in Operation Badger Catch III from 28 April – 3 June. It then moved to Đà Nẵng and prepared for Operation Swift Saber which took place from 7–14 June. Landing Exercise Hilltop XX occupied the ship early in July. Then Valley Forge transferred its Marines and helicopters to Tripoli and headed home via Hong Kong, Okinawa, and Pearl Harbor. She reached Long Beach on 3 August.
Following five months on
USS Valley Forge (CV-45)