The most important change for this title is the shift to an open world design with a real-time day and night cycle, doing away with the linear mission approach of previous games. The protagonist, Big Boss (Snake), works with Militaires Sans Frontières and needs to infiltrate an American black site Camp Omega on Cuba.
The game offers the single objective to free two held characters, Paz and Chico, and the player determines the approach. Snake can use various tools to aid him in his mission, such as a handheld device that displays a map of the base and allows him to check mission information. The game also features a more direct approach with guns and explosives.
With a stealth approach, enemies can be knocked out or taken down with a knife, while using a third-action shooter approach, many means can be found inside the camp, including turrets and guns. Enemies have a line of sight, and Snake can stay hidden through crouching. Once detected, enemies become suspicious and need to be tracked down.
Four additional side missions can be unlocked in the same location but set before the main mission. A fifth one becomes available after collecting all XOF patches, and it is different depending on the system used.