Cheating in poker is any action outside the rules and regulations which is taken to give an unfair advantage to one or more players. The cheating is generally grouped in hard and soft cheating. An example of hard cheating would be the distinction in mechanics, collusion, and the like and soft cheating would be noting the bottom card that the dealer happened to expose without calling for a misdeal. While the rules are explicit on the subject of cheating in general, many otherwise fair players are tempted to "soft cheat". Miscalling your four hearts a flush is cheating, while offering alcoholic drinks is not, because each player can decline.

Cheating is more common in poker than most people would care to believe. While most cheating occurs in private games that do not follow strict gaming procedures, it is also very common in regulated card rooms and casinos or online poker sites. Cheating can be done either by means of collusion, sleight-of-hand (such as bottom dealing, stacking the deck, switching cards etc), or the use of cheating gaffs (such as marked cards, holdout devices, etc).

A card cheater may operate alone, but most of them operate in pairs or small groups. The groups are often composed of one card mechanic who is in charge of manipulating the cards, one or several shills who pose as regular players, and a muscle who acts as a bodyguard. Street gangs also often employ a wall man who acts as a lookout.

Following is a list of terms used to categorize specific card cheaters:

Card Mechanic A card cheater who specializes in sleight-of-hand manipulation of cards.
Base or 2nd Dealer Also called bottom dealer/second dealer is a cheat that specializes in bottom/second dealing.
Paper Player A card cheater that exploits the use of marked cards.
Hand Mucker A card cheater who is an expert in switching cards.
machine player A card cheater that uses mechanical holdouts.
Crossroader Traditionally, any kind of traveling hustler. Now the term is mainly use to describe cheaters who specialize in hitting casinos.
triple f**ker Describes how a player makes rude and loud noises to attract attention while he/she cheats.