Vessels sailing under the Montserrat Country Flag are required to have on board this flag as part of flag state requirements that derive from maritime regulations in the International Code of Signals and the International Safety Management (ISM) Code. These codes are published by the International Maritime Organization (IMO) as an ongoing effort to reinforce maritime safety procedures and communications to the international maritime community. Fleet management companies and ship owners are responsible to ensure that each vessel in their respective fleets have the appropriate flag signage onboard to be in compliance. This flag is used to identify the flag state a vessel is sailing under and to communicate with other vessels under the provisions of the International Code of Signals.

The Montserrat Country Flag is characterized by a royal blue background. The Union Jack representing the United Kingdom appropriates the upper hoist, or left side quadrant. The Montserrat Coat Of Arms is depicted centered in the fly, or right side half of the flag as defined from a vertical line drawn through the flag center. The Union Jack appears as a royal blue background with two diagonal red stripes outlined in white and crossing in the center. These are recessed behind a larger red cross outlined in white, the body stretching from top to bottom and the arms reaching the length of the flag from hoist to fly. The Montserrat Coat Of Arms depicts a ground and sky landscape. A woman is shown carrying a harp and embracing a passion cross. The Montserrat Country Flag was formally adopted in 1999 after some minor changes, however it was initially adopted in 1909. The Flag is designated to be proportioned at a ratio of 1:2, height to length, respectively. The Island was devastated by an ongoing massive volcanic eruption in 1995.