Details of the contract, including the number of units ordered and the schedule for their delivery, were not disclosed by the ministry.
Hellfire, made by the U.S. firm Lockheed Martin, is a proven tactical air-to-ground weapon with a range of about five miles. Apache attack helicopters can carry as many as 16 missiles at a time.
"Its successful use in Afghanistan and in training has reduced U.K. stocks of the missiles, which is why MOD has signed an order for more Hellfires," the ministry said.
"Hellfire has proved itself in Afghanistan and Libya, providing our Apache crews with state-of-the-art precision firepower," said Philip Dunne, minister for defense equipment, support and technology. "This order will ensure the Apache's attack capability remains in place for current and future operations."