Wolfenstein: The Old Blood changes little from the basic gameplay of The New Order. As such, it is an action-adventure shooter game played from a first-person perspective. To progress through the story, players take on enemies while navigating throughout levels. The game utilizes a health system in which players' health is divided into separate sections, "health" and "armour", that regenerate; if an entire section is lost, players must find and use a health pack or body armour piece, to replenish the missing health.
Players use melee attacks, firearms and explosives to fight enemies, and may run, jump and occasionally swim to navigate through the locations. Melee attacks can be used to silently take down enemies without being detected. Alternatively, players can ambush enemies, which will result in an intense firefight between the two parties. Enemy types vary; standard Nazi human soldiers, which vary in strength, mechanical robot-like characters, zombie Nazi soldiers, and vicious dogs are some of the enemies players will encounter.
In combat, a cover system can be used as assistance against enemies. Players have the ability to lean around, over, and under cover, which can be used as a tactical advantage during shootouts and stealth levels. Players have access to a weapon inventory, which allows the player to carry as many weapons as they find. With some of these weapons, players have the ability to dual wield, giving them an advantage over enemies by dealing twice as much damage. The Old Blood adds various weapons that were not featured in The New Order, such as a steel pipe. The steel pipe is one of the biggest additions to the game; it consists of two small steel pipes which can be connected together to make a larger pipe. Both pipe states can be used as a melee attacks (each with their own animations) and in specific circumstances; the two small pipes, called "Pipes" in the weapon inventory, can be used to climb rock walls, and the large pipe, called "Pipe" in the inventory, is used to break open weak environmental surfaces. The game gives players a wide variety of weapon options—they can be found on the ground, retrieved from dead enemies, or removed from their stationary position and carried around. Weapon ammunition must be manually retrieved from the ground or from dead enemies.
As with The New Order, players can complete "Perks"; each Perk has a task the player can complete. Perks encourage the player to change their play style on the fly; collecting "helmets", getting silent kills, killing specific enemies a select number of times, getting a set number of kills with a specific weapon, and getting kills via explosives are some of the objectives. Once a Perk's task is complete, the player unlocks a bonus, such as more overall health or armour, more ammunition for a certain weapon, or the ability to gain health after a silent takedown. Various collectibles are also scattered throughout the levels; concept art, character models and bios, notes, which tell small side stories of the game, and gold bars are some of the collectables.
Other modes in the game differing from the main chapters are Challenge Arenas and Nightmare Levels; Challenge Arenas unlock as the player progresses through the story and are accessed from the main menu. Being a basic arena battle mode, players fight waves of enemies to obtain a Bronze, Silver, or Gold metal. Nightmare Levels are accessed by finding and interacting with a bed that is hidden in each chapter. Gameplay is very similar to Wolfenstein 3D; the player moves through pixelated hallways, mostly equipped with just a pistol, fighting Nazi soldiers. The objective is to find a key that unlocks an elevator.[14