The item must be equipped in the Action slot of the class the player is currently using, or can be activated from the Backpack by selecting the item and clicking the Use button while connected to a server. When activated, the game will inquire if the player wants to challenge someone on their friends list, who needs to be playing Team Fortress 2 at the time, or someone on the server they're currently on. A notification will pop up when the challenge is activated, and the selected player will then choose to accept or deny the challenge. When activating a duel, the challenger has the option of selecting a class-locked duel. If a class-locked challenge is accepted, both players are locked to that class for the entire game (The class-selection screen can be opened, but changes won't take effect). If the player challenges someone on a server, everyone currently in the server will be notified. A player may only be in one duel at a time, but there may be multiple duels going on in a server at once.
If both players accept, the duel begins. This item will not be consumed if the other player refuses the duel. At the end of the round, whoever has more duel points wins. Kills and assists against the opponent, including "finished off" credited kills, are worth 1 point.
The item's quantity is not reduced if the server changes level, one of the players is kicked, or the score is tied.
When a duel is accepted or rejected, the classes involved may speak special responses.
The duel leaderboard can be seen here, which lists the players with the most duel wins.
Each day, the person worldwide with the most duel wins from the previous day is given the Dueler hat.
The goal is to obtain Duel Points by killing the opposing duelist or assisting in their death. The player's opponent will have an icon above his head to identify him, similar to a domination. The Scoreboard will also change to show the amount of Duel Points of each player, replacing the usual information available through it. In addition, both parties will be notified via pop-up message with each point scored.
Whoever has more duel points by the end of the round wins. Alternatively, if one of the duelists leaves the server or changes teams, their opponent wins, regardless of whether or not they change back or reconnect (including use of the 'retry' console command).
The Dueling Mini-Game is canceled if one of the duelists is kicked or forced into another team (as a result of automatic balancing, for example), the server resets, or the map changes, although the duel continues if players vote to restart the map. If both player score the same amount of points when the round ends, the Dueling Mini-Game item is not consumed.
Cues are taken from the song Playing With Danger.
- Unrestricted duel initiated.‡
- Class restricted duel initiated.‡
- Duel challenge has been accepted.
- Class restricted duel challenge has been accepted.
- Duel challenge has been declined.‡.
- Class restricted duel challenge has been declined.‡
- Duel challenge score has been updated.
- Duel challenge score has been updated where you are behind.
‡Accompanied by a class response.
Regardless of the result, upon completing their first duel the player is given the Bronze Dueling Badge. The badge will also level up with every tenth win. When this happens, the player gets a random item along with another "Dueling Mini-Game" with 5 uses. These items are announced to the server as "%playername% has earned: %itemname%", rather than the usual "has found" template. At levels 25, 50, and 75 the badge will increase in quality. After that, the badge will continue to climb in levels up to level 100, but will no longer change. Dueling badges currently only show wins, not losses.
| Level 1
(play a duel)
|Bronze Dueling Badge|
| Level 25
(win 240 duels)
|Silver Dueling Badge|
| Level 50
(win 490 duels)
|Gold Dueling Badge|
| Level 75
(win 740 duels)
|Platinum Dueling Badge|
- If the teams are scrambled after a duel is set up, both duelists may be on the same team, but the duel is not ended.
- If two or more duels are going on concurrently in a server and one of them ends, the other duels may have their scores locked; the scoreboards of the remaining duelists will go back to normal, but the duels will only actually conclude when they would normally do so (if the round ends, etc.).
- If a Spy disguises as a player with the Dueling Mini-Game equipped in their action slot, pressing the action key will bring up the duel prompt, even if the Spy player does not have it equipped. However, selecting a player from the prompt will do nothing.
- Both the in-game leaderboard and the online leaderboard are currently frozen and have been for some time; however, both dueling and the dueling badge still work correctly and the badge will level up after 10 duel wins.
- If the badge is deleted, a new one will be awarded upon completing another duel. This new badge will have the same stats as the old one, but with a new "date received".
- It was stated in an interview with Gabe Newell that the Dueling Mini-Game spun-off from a full game mode idea. Gabe Newell also hinted at the possibility of adding other mini-games in the future. 
- PCGamer Interview: Valve on why they’re selling TF2 items for real money, Retrieved 2011-03-24.
- Interview: Which Team Fortress 2 item are worth your money