Gears of War 4 is the fourth main game in the series and aside from some early work it no longer involves the original developer Epic Games for the first time. It is set 25 years after the end of the Pendulum Wars between the Coalition of Ordered Governments (COG) and the Union of Independent Republics, the two superpowers of the planet Sera who fought for control over the natural resource "immulsion". Three of these battles are part of the interactive introduction mission of the game. The war was ended when COG gained the advantage, but it was immediately followed by a Locust attack on what is known as Emergence Day or E-Day. This ended in the destruction of all immulsion resources with the Immulsion Countermeasure weapon, which also took out the Locust and the Lambent. The aftermath has led to a society with a reformed COG with only hundreds of thousands of humans left, but void of fossil fuel and with powerful "windflare" storms that form across the planet Sera where the game takes place. To prevent the population from declining, cities are now walled off to prevent against outside danger. This has also led to the formation of Outsiders. These are survivors that reject the COG rule and live outside of the jurisdiction, conducting raids for resources.

The game's story campaign focuses on J.D. Fenix, son of Marcus Fenix and Anya Stroud from the earlier games, together with his friends Delmont Walker and Kait Diaz. Early on they join an Outsiders group led by Reyna to get away from COG rule. They assist with raids and acquiring technology, until they are eventually attacked by unknown creatures dubbed The Swarm. This leads J.D. to reluctantly ask for the help of his father to identify and defeat the creatures. Next to Marcus, this brings back other known characters as well, such as Cole, Baird and Sam.

The gameplay relies on the familiar cover shooter mechanics. Dynamic covers now include boom shields, meat shields, and pods that can shot and sometimes contain an enemy. The game's windflares play a role now, as grenades and other projectiles, but also character movement, is affected during storms. The main opponent is The Swarm, with character types such as Carriers, Drones, multiple types of Juvies, Pouncers, Snatchers (mostly a mini-boss) and more. They use similar weapons as they also rely on COG technology and employ similar tactics as the humans as well. Usually there is a party of three members and next to Fenix another character, usually Del or Kait, can be controlled by a second, human player. When playing alone all other characters are controlled by the AI. As usual only two weapons can be carried, with classic weapons such as the Lancer with its chainsaw. There are now two versions of the weapons, using the same ammo, as well as two types of sniper rifles, the Hammerburst, the Marzka MK1 and more. The Buzzkill is a new type of weapon that fires saw blades. Other new weapons are the Dropshot, EMBAR and Enforcer. A pistol and grenades can be used in addition, along with melee attacks and executions. It is now possible to slide over cover and vault kick enemies on the other side. Ammo is relatively scarce, so often weapons dropped by enemies need to be picked up.

Next to cooperative campaign for multiple players, the Horde multiplayer mode is featured for the third time, fighting 50 waves of enemies with up to five players working together. Some of this wave-based gameplay is also incorporated in segments of the regular campaign. New elements for the 3.0 version are skill and ability progression. Instead of the static locations near a command post in the previous game, players can now use a Fabricator to construct defenses, fortifications and weapons any where on the map. Characters can receive bonuses to statistics and abilities using Gear Cards. Unlocks and rewards are not based on level progression. Instead all action is rewarded with credits used to acquire Gear Packs with different types of content such as weapons and skins. Cards can be discarded for a different currency, Scrap, which in turn can be used to create almost any card in the game. Packs and other currency elements can also be bought straight away with real money.

Different modes are now part of Core and Competitive playlists. The latter have a higher difficulty level, putting more emphasis on team play by toning down damage or affecting aim assist. There is also a Social playlist where the Core modes are mixed and players can vote. Multiplayer modes include Arms Race, Dodgeball, Escalation, Execution, Guardian, King of the Hill, Team Deathmatch, and Warzone. Escalation and Execution are exclusive to the Competitive playlist. The game was launched with ten multiplayer maps. There is cross-platform multiplayer, but only for cooperative games, not competitive ones.