Gules, a pale Argent, on a chief of the like a fleur-de-lis of the first.
On a wreath of the colors Argent and Gules, a tower of five merlons of the first, masoned Azure, bearing an arrowhead in base, point up, tierced per fess of the second, Vert and of the second charged with a mullet Or, all below and supporting a lion's head erased of the last langued of the third and charged with an arrowhead point up of the last.
CONDITE ET PUGNATE (Build and Fight).
The shield is red and white for Engineers, while the fleur-de-lis represents service in France during World War I.
The tower represents fortification and engineering. The five battlements allude to the Battalion's five decorations. The lion and blue arrowhead symbolize the Battalion's Presidential Unit Citation awarded for the assault landing at Normandy. The green and red arrowhead on the white tower refers to the assault landing in Sicily (red, white and green are the National colors of Italy). The colors red and green and the gold star also allude to the award of the French Croix de Guerre for the action at Vierville-Colleville. Gold and red refer to the colors of the Republic of Vietnam where the unit received three Meritorious Unit Commendations.
The coat of arms was originally approved for the 20th Engineer Regiment on 11 April 1941. It was amended to correct the blazon on 19 May 1941. It was redesignated for the 20th Engineer Combat Battalion on 11 June 1951. It was redesignated for the 20th Engineer Battalion on 12 October 1956. It was amended to add a crest on 21 May 1973. The insignia was amended to correct the Latin translation of the motto on 19 March 1974. It was amended to correct the symbolism of the crest on 24 October 1975.