Hailing from an indeterminate region of France, the Spy is an enthusiast of sharp suits and even sharper knives. Using a unique array of cloaking watches, he can render himself invisible or even fake his own death, leaving unaware opponents off-guard. His Disguise Kit lets him take on the form of any class on either team, allowing him to blend in while behind enemy lines before stabbing his unsuspecting "teammates" in the back. In fact, a swift backstab with any of the Spy's knives will kill most foes in a single hit - provided they aren't under the effects of any type of invulnerability, or some other form of immense damage reduction.

In addition to being able to swiftly assassinate key enemies, the Spy possesses the ability to disable and destroy Engineer-constructed buildings with his Sapper. Once attached to an enemy building, the Sapper disables and slowly drains health from the building. However, a Sapper can be removed by an Engineer, or Pyro wielding the Homewrecker, Maul, or Neon Annihilator.

The Spy is able to enter an enemy teleporter and can use this to make his way to the enemy team, and blend in amongst them.

Whereas most players can only see the names and health of their teammates, the Spy can observe the names and health of the enemy team as well, allowing him to relay useful intelligence. This ability is unique to only the Spy and a Medic carrying the Solemn Vow.