William, second in line to the throne and the eldest son of Prince Charles and his deceased first wife Princess Diana, will co-pilot Sea King helicopters as part of a four-man crew based at RAF Valley in Anglesey on the north west coast of Wales.
"The course has been challenging, but I have enjoyed it immensely," said William, 28, who now has the rank of Flight Lieutenant.
"I absolutely love flying, so it will be an honour to serve operationally with the search and rescue Force, helping to provide such a vital emergency service."
The prince completed 70 hours of flying time augmented by 50 hours in a simulator as part of training to get to grips with the helicopter.
William's younger brother Harry has served on the front line in Afghanistan with the British armed forces.