Gules, within a bordure indented the Roman numeral III Argent.
On a wreath of the colors Argent and Gules a beaver couchant at the foot of a palm branch Proper.
BUILDERS FOR VICTORY.
The shield is red bordered with white, the Engineer colors, the border being indented in allusion to the Engineer work in connection with field intrenching.
The beaver is the old symbol of New York dating from 1623, when it was on the arms of New Netherlands, and is now on the seal of New York City. The palm branch is symbolic of tropical service.
The coat of arms was originally approved for the 3rd Engineer Regiment on 11 February 1921. It was redesignated for the 3rd Engineer Battalion on 11 March 1942. The insignia was redesignated for the 3rd Engineer Combat Battalion on 31 January 1950. It was redesignated for the 3rd Engineer Battalion on 30 October 1958. The coat of arms was amended to add the motto on 2 February 1967.