Days Gone is an action-adventure game set in a world ravaged by a global pandemic that has turned most of humanity into zombie-like creatures. The protagonist, Deacon St. John, lost his wife to the pandemic and now lives as a drifter with his old biker gang buddy, Boozer. The main storyline features several playable flashbacks that tell more about events before the pandemic, while the side quests are presented as stories with their own progress trees. The player's actions can affect and progress multiple storylines simultaneously, and some missions and events can be completed at any time.
Days Gone ' world map is divided into three sections, each of which reveals itself gradually throughout the game. The map shows refugee camps, bandit camps, NERO checkpoints, and other areas of interest, while also highlighting currently active missions on the world map.
Deacon can earn experience points by killing infected or bandits, as well as completing quests. As he earns experience points, his character levels up, unlocking new skills in one of three skill trees: Melee, Ranged, and Survival.
Bike upgrades work differently in the game, with each settlement having its own currency and trust levels. Deacon can earn credits by selling ears collected from killed infected or by completing tasks for settlements, which increases his trust level and earns him more credits to spend.
Days Gone ' combat system allows Deacon to carry four different weapons of varying types, each with its own durability and strength. He also carries a boot knife for stealth kills or when no other blunt weapon is available. Scavenging in the game involves finding new weapons and objects to fight with, as well as gathering resources like gas, band-aids, and medkits. Deacon can use his skills and tools to pry open car hoods and take necessary parts from their engines.