In Mystery Heroes, players cannot select their own hero.
- The "Assemble Your Team" section is skipped upon starting a game.
- Players will be assigned a random hero upon entering a game and every time they respawn, with their ultimate meter being reset. A player cannot respawn as the same hero they were when they died.
- An exception to this is when a player kills themselves. They will respawn as the same hero, but any buildable objects on the map will disappear and their ultimate meter will still be reset.
- Because of the randomly-assigned hero mechanic, hero stacking is allowed.
During the Winter Wonderland seasonal event, Mystery Heroes is changed to Winter Mystery. It plays identically to the standard, but the only maps available are King's Row (Winter) and Hanamura (Winter).