The Commissioner is appointed by the British monarch on the advice of the Foreign and Commonwealth Office.

This involves the passing of any necessary legislation for the territory, usually Orders in Council or Statutory Instruments.

The Commissioner is also responsible for liaising with the military of the United States in matters concerning the territory.

An Administrator of the British Indian Ocean Territory acts as the Commissioner's assistant.

The Commissioner also appoints a representative on the territory, who is the senior British military officer at Diego Garcia.