The offical currancy is the Caymen Dollar.

In 1971, the first Cayman Islands currency was issued. The Currency Committee which was formed prior to 1971 to consider the introduction of Cayman currency decided upon a decimal system of currency consisting of four notes of $1, $5, $10, and $25, and four ordinary circulating coins of the following denominations - 1 cent, 5 cents, 10 cents and 25 cents. In 1981 the Board introduced the new denominational values of $100 and $40 notes followed by the issue of the $50 note in 1985. The contracts for printing the notes and minting the coins continue to be awarded to Thomas De La Rue and Company Limited and The British Royal Mint, respectively. Today, the Cayman Islands Monetary Authority is the organization responsible for the issue and redemption of Cayman Islands Currency.
Today, the Cayman Islands Monetary Authority is the organisation responsible for the issue and redemption of Cayman Islands Currency.

Central Bank Website