A silver color metal and enamel device 1 1/8 inches (2.86 cm) in width overall consisting of a maroon cross surmounted by a voided silver five-pointed star and charged in base by a silver Philippine sun, all above and between a blue scroll bearing the inscription "RIGHTFULLY PROUD" in silver letters.

Maroon and white are the colors used for Medical organizations.  The five-pointed star symbolizes health and wisdom and refers to King Solomon's seal, symbolizing the unit's service in Northern Solomons.  The Philippine sun refers to the Philippine Presidential Unit Citation awarded to the organization for its World War II participation.

The distinctive unit insignia was originally approved for 31st Surgical Hospital on 16 May 1969. It was redesignated for the 31st Combat Support Hospital on 9 February 1973. It was redesignated for the 131st Field Hospital with the description and symbolism revised on 1 February 1995. The insignia was redesignated for the 31st Combat Support Hospital on 16 October 2005.  On 17 April 2018, the DUI was redesignated for the 131st Field Hospital.