A gold color metal and enamel device 1 3/16 inches (3.02 cm) in height overall consisting of a white stylized cinquefoil bearing a gold wheel, with four spokes exposed, surmounted by a Greek maroon cross charged from the upper left angle to the lower right angle with a diagonal white wavy band.
The wavy diagonal representing water and its central location refers to the unit's participation in the Rhineland and central Europe Campaigns during World War II. The wheel alludes to the semi-mobile and evacuation capabilities of the Hospital. The cross, a sign of aid and assistance, symbolizes the Hospital; and the stylized cinquefoil representing the Mayflower (the Massachusetts State Flower) symbolizes the home station of the unit at Taunton, Massachusetts. Maroon and white are colors used by the Army Medical Department.
The distinctive unit insignia was originally approved for the 399th Evacuation Hospital on 11 February 1971. It was redesignated for the 399th Combat Support Hospital on 8 November 1976.