The airport began during World War II as Pinecastle Army Airfield, an auxiliary airfield to Orlando Army Air Base, now known as Orlando Executive Airport. At the end of the war, Pinecastle was briefly used for unpowered glide tests of the Bell X-1 from B-29 aircraft before the program moved to Muroc Army Airfield in California — now Edwards AFB — for the world's first supersonic flight. Briefly placed in caretaker status, the base was reactivated during the Korean War for use as a Strategic Air Command (SAC) facility for B-47 Stratojet and KC-97 Stratotanker aircraft. As an Air Force facility, it was renamed Pinecastle AFB.
In the early 1960s, when commercial jet airline service came to Orlando, the installation became a joint civil-military facility. First-generation commercial jetliners such as the Boeing 707, Boeing 720, Douglas DC-8 and Convair 880 required longer and sturdier runways than the ones at Orlando Municipal Airport (now Herndon Airport). Nearby lakes and commercial and residential development made expansion impractical, so an agreement was reached between the city of Orlando and the U.S. Air Force in 1962 to use McCoy AFB under a joint civil-military airport arrangement. The military offered a large AGM-28 Hound Dog missile maintenance hangar and its associated flight line ramp area in the northeast corner of the installation for conversion into a civilian air terminal for the city. The city would then cover the cost of building a replacement missile maintenance hangar on the main base's western flight line. Once executed, the new civilian facility would be known as the Orlando Jetport at McCoy and would operate alongside McCoy AFB. This agreement became a model for other joint civil-military airports in operation today.
In 1975, the final Air Force contingent departed McCoy and the Greater Orlando Aviation Authority (GOAA) was established as a state-chartered governmental agency and an enterprise fund of the city of Orlando. GOAA's mission was to operate, manage and oversee construction of expansions and improvements to both the Orlando International Airport and the Orlando Executive Airport. The airport gained its current name and international airport status a year later in 1976, but retained its old IATA airport code MCO and ICAO airport code KMCO.
In 1978, construction of the current Landside Terminal and Airsides 1 and 3 began, opening in 1981. The original International Concourse was housed in Airside 1 and opened in 1984. Funding to commence developing the east side of the airport was bonded in 1986, with Runway 17/35 (now 17R/35L) completed in 1989. Airside 4 opened in 1990 and also contains an International Concourse for the processing of international flights. Airside 2, which filled out what will become known as the North Terminal complex, was completed in 2000, with the last additional gates added in 2006. Runway 17L/35R was opened in 2003, providing the airport with a total of four runways.
On February 1, 2010, Allegiant began operations at the airport. The company moved one half of its Orlando Sanford International Airport (SFB) schedule to Orlando in order to test revenue streams at the higher cost airport. After evaluating the routes out of Orlando, the carrier decided to consolidate and return its Orlando area operations to SFB citing an inability to achieve a fare premium at MCO as anticipated, a strong passenger preference for Orlando Sanford International Airport, higher costs at MCO than expected and a more efficient operating environment at SFB.