A variable displacement pump includes a rear cover and side plate arranged on both sides of a cam ring and making slide contact with the cam ring. The rear cover has an end face on the side of the cam ring, which is formed with a suction port. A seal member is arranged in a chamber formed between a pump housing and the cam ring and for dividing the chamber into two portions that define first and second working chambers. A connection groove and terminal groove are formed in the end face of the rear cover to provide fluid communication between the suction port and the second working chamber.