Gules, a chevron Or charged with a pine tree Vert, in base a bear statant of the second (Or).
That for the regiments and separate battalions of the Army Reserve: On a wreath of the colors 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 shield is red for Artillery, the gold chevron and the green pine tree indicate the service in France in the 91st Division. The golden bear indicates that the regiment is allocated to California.
The crest is that of the United States Army Reserve.
The coat of arms was originally approved for the 346th Field Artillery Regiment on 16 March 1925. It was redesignated for the 346th Field Artillery Battalion on 3 October 1942. The insignia was redesignated for the 91st Regiment on 30 January 1962.