Cheating in poker is any behavior outside the rules that is intended to give an unfair advantage to one or more players.

Cheating can be done many ways, including collusion, sleight-of-hand (such as bottom dealing or stacking the deck), or the use of physical objects such as marked cards or holdout devices.

Skilled methodsA cheat may hand-muck, that is, switch their hand with one they have secretly hidden. This may also be done with a confederate.

A skilled cheat can deal the second card, the bottom card, the second from bottom card, and the middle card. The idea is to cull, or to find the cards one needs, place them at the bottom, top, or any other place the cheat wants, then false deal them to oneself or one's confederate.

One sign of false dealing could be when a dealer grips the deck with the index finger in front of it. This is referred to as the mechanic's grip. It not only allows better control of the cards, but provides cover by showing the back of the top card, and without moving the hand holding the deck.

Even if a cheat deals himself a powerful hand, he may not win much money if every other player has nothing, so often the cheat will stack two hands, with one player getting a strong hand and the cheater getting an even stronger one. This is called a double duke.

One method of cheating that involves both great risk and great potential pay-off is the cold deck—so called because it has not been "warmed up" by play (and thus randomised). Such decks are usually pre-stacked, and are introduced either at the deal, after the real deck has been shuffled, or before the deal, where a card sharp will make a false shuffle using sleight of hand. The latter method may require collusion or a pass if the style of play or house rules call for a cut. The skill lies both in convincing other players that the shuffle is legitimate and in ensuring that other players receive hands that are good enough to entice them into play, but not too good to arouse suspicion.

Marked cards

Marked cards are printed or altered so that the cheater can know the value of specific cards while only looking at the back. Ways of marking are too numerous to mention, but there are certain broad types. A common way of marking cards involves marks on a round design on the card so as to be read like a clock (an ace is marked at one o'clock, and so on until the king, which is not marked). Shading a card by putting it in the sun or scratching the surface with a razor are ways to mark an already printed deck.

Juice and "daub" are two kinds of substances that can be used to mark cards in a subtle way so as to avoid detection, when done properly. While a "juice" deck is premarked and introduced into play by the cheater, "daub" is applied during play to any deck. Once trained, cheaters can read the cards from across the table.

Decks can be marked while playing using fingernails or by bending or crimping the cards in a position that the cheat can read from across the table. The practice of burning the top card, or cards, is to prevent a cheat from knowing that top card and dealing "seconds" to either give a confederate a card that helps his hand or an opponent a card that hurts his.

Minimal-skill methodsThe easiest and most common types of cheating require no ability of manipulation, but rather merely the nerve. Such methods include shorting the pot, avoiding house fees, and peeking at other players' cards. However, it is very difficult to prove because when confronted, at least the first time, the cheat often calls the cheating an honest mistake.

One minimal-skill method that occurs in non-casino games happens when a player who has folded appoints himself the tender of the pot, stacking chips, counting them, and delivering them to the winning player. Check-chopping is when such a "helpful" player palms a chip. Odorless adhesive can be used for this purpose.

Another minimal-skill method is going south (also known as "ratholing"), where a player covertly removes a portion of his chips from play while remaining in the game, normally in order to preserve the winnings as profit, or prevent a major loss in "big bet" games.