On 20 August 1971, the 20th Engineers cased its colors in the Republic of Vietnam and moved to Fort Campbell, Kentucky, where it took the place of the recently deactivated 51st Engineer Battalion. Very few soldiers actually moved to Fort Campbell; most soldiers were re-distributed to other units in Vietnam, and the unit in place at Fort Campbell basically replaced the colors of the 51st Engineers with the colors of the 20th Engineers.

Throughout 1971 the 51st Engineers, then the 20th Engineers, conducted normal training and construction operations at Fort Campbell. The companies executed various post projects, conducted NBCAIC (Nuclear, Biological, Chemical Accident/Incident Control) alerts, executed building improvements, conducted 24-hour alerts, and went on short field training exercises. Each of the companies reported severe manpower shortages in their October histories. In a relief attempt, soldiers from the 173rd Airborne Brigade who refused jump status were reassigned to the 20th. Though this was a temporary fix in numbers, these soldiers were not up to the Engineer standard and many were AWOL within just a few months.

In 1972, the 20th Engineers completed construction projects on Fort Campbell including ranges, heliports, ammunition supply points, tank trails, and stockade building rehabilitation. Company D also worked on a civic action project in the Bowling Green, Kentucky community. The company constructed a recreation park, cleared debris, constructed a foot bridge, installed culverts and constructed picnic tables. HHC provided construction expertise to the Hopkinsville, Kentucky Senior Citizen's Center by constructing a wood-working shop, roof renovations, and wiring and hanging florescent lights.

Also in 1972, the Battalion participated in Operation Flamingo at Homestead Air Force Base, Florida. The operation involved loading 88 aircraft with soldiers, vehicles, and equipment as a deployment readiness exercise. The Battalion was still critically short soldiers and reported only a 35% fill of mechanics in October 1972. That same month the 114th Engineer Detachment (Fire Truck) and the 26th Engineer Detachment (Water Purification) were attached to the 20th Engineer Battalion. Construction projects in Flatwoods, Tennessee, Clarksville, Tennessee, and Eddyville, Kentucky were completed as part of a Civic Action Program.

On 29 May 1973, the 20th Engineer Battalion was the first non-divisional unit at Fort Campbell to receive the coveted Commanding General's Outstanding Unit Award. The battalion completed the Indian Mound Airfield for Fort Campbell in 1973. Company B and elements of the 326th Engineer Battalion reshaped and recrowned the runway and conducted rock crushing operations in preparation for Operation Brave Shield VII. The project also supported Operation Orbiting Eagle II in mid-November 1973.

Civic Action Projects were at the forefront of 20th Engineer Battalion missions throughout 1973 and 1974. The following projects were completed:

• West Point, GA - demolition of 1000 foot long, 85 foot high Seaboard Coastline Railroad Bridge spanning the Chatahoochee River
• Cleveland, TN - county recreation area including athletic fields and picnic areas
• Clarksville, TN - Fairgrounds Park