Gules, on a pile wavy Or, a pine tree eradicated Azure, in base two fire arrows point up of the second enflamed Proper.
On a wreath Or and Gules an isosceles triangle of the first, bordure of the second bearing between a pellet from which issues an arrow with doubled barbs palewise Sable and the Arabic numerals "55" Gules, a caterpillar fesswise of the last, all conjoined.
Red and yellow are the colors of the Artillery branch. The wavy pile alludes to the unit's origin as Coat Artillery and further suggests service across two oceans, noting that the 55th Artillery campaigned in both the European and the Pacific theaters. The fire arrow, a highly effective artillery weapon of pre-gunpowder days is an allusion to the firepower of present day artillery; the two of them representing participation in both World Wars. The blue pine tree denotes award of the Distinguished Unit Citation for the Ardennes Campaign of World War II.
The 55th Artillery Regiment was organized in 1918 from both regular and National Guard Coast Artillery Companies. One of the companies was from the "Old First" Regiment of Massachusetts whose motto was Vigilantia. The Regiment saw heavy service during World War I and was armed with 155mm guns and caterpillar which are represented in the design.
The coat of arms was originally approved for the 55th Artillery Regiment on 8 March 1922 and consisted only of the badge (DUI) as the crest of the coat of arms. It was redesignated for the 55th Field Artillery Battalion on 25 June 1952. It was redesignated for the 55th Artillery Regiment on 17 December 1958. The coat of arms was amended to add a shield on 8 July 1965. It was redesignated for the 55th Air Defense Artillery Regiment on 14 January 1972.