The Hospital was activated in Australia in 1942 as the 3rd Portable Hospital. The unit served in the Southwest Pacific until it was inactivated in the Philipines in November, 1945.

In May 1949, it was reactivated as the 3rd Mobile Army Surgical Hospital at Fort Meade, Maryland and was sent to Eniwetok Atoll to provide medical support to military personnel stationed there. The Hospital operated a dispensary in Eniwetok from March to October, 1950. The Surgical and Ward Sections were located on a ship, the USS APL 27, anchored off shore until permanent buildings were completed ashore.

The Hospital again was returned to the United States in 1951 and eventually returned to Fort Meade, Maryland in 1954. The Hospital served in a training status and in various support roles, including medical support for forest fire fighters, establishing exhibits and evacuation demonstrations, and providing support for units during summer training. In May 1965, the unit was alerted for movement to Vietnam.

The first patient was seen on 18 September 1965, at the Hospital site at Bien Hoa, Republic of Vietnam.

The unit became Air Mobile in February 1966. Between February and April that year, the Hospital supported Operation Garfield in the Ban Me Thuot area, and returned to Bien Hoa on 9 April 1966.

Construction on a new hospital complex was completed in July 1966. The new facilities allowed patients to be treated in air conditioned buildings to negate high temperature and humidity.

The Hospital operated at Bien Hoa until April 1967. The unit moved to Dong Tam Base in May 1967 as a MUST unit. On 1 June, the first patient was received in support of the 9th Infantry Division.

The Hospital was removed from 1st Logistical Command and placed under HQUSARV, as part of the 44th Medical Brigade, under the 67th Medical Group in September and October 1967. The 346th Medical Detachment (MA), Can Tho, was attached for administrative control on 23 October 1967.

Shrapnel from the frequent mortar and rocket attacks on Dong Tam Base Camp often punctured the inflatable MUST units, seriously hampering operations. This necessitated a self-help program to cover all MUST elements with earthfilled revetments. A severe mortar attack on 24 July hurried the construction plans and the revetments were completed in September 1967. The Hospital was assigned to the 68th Medical Group, 16 February 1968. The 3rd Surgical Hospital closed out its operations in Dong Tam during the Summer of 1969, when the 9th Infantry was returned to the United States.

In August 1969, the unit moved to Binh Thuy and was attached to the 29th Evacuation Hospital (SMBL). It assumed operational control of the hospital facilities of the former 29th Evacuation Hospital and its attached units (346th Med Det (MA) and 43rd Med Det (RB) on 1 October 1969.

The 3rd Surgical Hospital (MA) and attached units operated a 75 bed hospital at Binh Thuy in support of United States Army personnel, other US and Free World Military Assistance Forces personnel, Civilian War Casualties, and Civilian Irregular Defense Group (CIDC) personnel as directed by higher authority.