Gules, between two fleurs-de-lis in base a pile Or, thereon a grenade Sable enflamed of the field.
That for the regiments and separate battalions of the Army Reserve: From a wreath Or and Gules, the Lexington Minute Man Proper. The statue of the Minute Man, Captain John Parker (H.H. Kitson, sculptor), stands on the common in Lexington, Massachusetts.
The grenade simulates the action of the organization during World War II, with the fleurs-de-lis representing the campaigns of Normandy and Northern France; they also allude to the name of the unit's first place of activation, Flora, Mississippi.
The crest is that of the U.S. Army Reserve.
The coat of arms was approved for the 398th Support Battalion effective 16 April 2007.