In Medieval times, warships had a single deck, with raised structures (the "forecastle" and "sterncastle") at each end. Following the introduction of cannon, the sterncastle was gradually replaced with a simpler structure consisting of the halfdeck above the main deck, extending forwards from the stern to the mainmast; and above that the quarterdeck, extending about half as far forwards. Later the halfdeck was extended the entire length of the ship, becoming the main deck (the former main deck now being the gun deck), leaving the quarterdeck as the only significant deck above the main deck.

The captain or master commanded the ship from the quarterdeck. The quarterdeck was traditionally the place where the captain walked when on deck, usually on the windward side. The navigator also used it when taking his sights when fixing the vessel's position. On most ships, it was customary that only officers could use the quarterdeck, others being allowed there only when assigned for specific duties. By extension, on flush-decked ships the after part of the main deck, where the officers took their station, was also known as the quarterdeck. This is the origin of the quarter berth - a single bunk tucked under the cockpit, usually found in smaller boats where there is not room for a cabin in this location... Preferred by some skippers as they can be close to the cockpit.