Shield
Per bend radiant, Gules and Argent, on the first a fleur-de-lis of the second, on the last an erupting volcano Proper.
Crest
On a wreath of the colors Argent and Gules, a dolphin naiant embowed of the first in front of a hurst of three coconut palm trees Proper.
Motto
DEFEND AND BUILD.
Shield
Scarlet and white are the colors of the Corps of Engineers. The erupting volcano signifies the power and energy of the organization. The per bend division of the shield is the heraldic representation of the scarf of a military commander. The rays of identification denote the force and speed by which the organization operates. The white fleur-de-lis symbolizes service in France in World War I.
Crest
The organization's three campaign awards for World War II service in the Pacific Ocean area are commemorated by the three coconut palm trees and the dolphin. The speed of the dolphin and its ability to rise from the water also connote the skill of the organization in performance of its engineering capabilities.
The coat of arms was originally approved for the 34th Engineer Regiment (Combat) on 9 February 1943. It was redesignated for the 34th Engineer Combat Battalion on 26 June 1944. The insignia was redesignated for the 34th Engineer Battalion and amended to add a crest and change the motto from "PAA I KA HANA (Hawaiian: "Busy" or "Secure in Work") to "Defend and Build" on 16 March 1967.