The history of poker is a matter of some debate. The name of the game likely descended from the French poque, which descended from the German pochen ('to knock'), but it is not clear whether the origins of poker itself lie with the games bearing those names. It closely resembles the Persian game of as nas, and may have been taught to French settlers in New Orleans by Persian sailors. It is commonly regarded as sharing ancestry with the Renaissance game of primero and the French brelan. The English game brag (earlier bragg) clearly descended from brelan and incorporated bluffing (though the concept was known in other games by that time). It is quite possible that all of these earlier games influenced the development of poker as it exists now.

English actor Joseph Crowell reported that the game was played in New Orleans in 1829, with a deck of 20 cards, four players betting on which player's hand was the most valuable. Jonathan H. Green's book, An Exposure of the Arts and Miseries of Gambling (G. B. Zieber, Philadelphia, 1843), described the spread of the game from there to the rest of the country by Mississippi riverboats, on which gambling was a common pastime. As it spread up the Mississippi and West during the gold rush, it is thought to have become a part of the frontier, pioneering ethos.

Soon after this spread, the full 52-card English deck was used, and the flush was introduced. During the American Civil War, many additions were made, including draw poker, stud poker (the five-card variant), and the straight. Further American developments followed, such as the wild card (around 1875), lowball and split-pot poker (around 1900), and community card poker games (around 1925). Spread of the game to other countries, particularly in Asia, is often attributed to the U.S. military.

The game and jargon of poker have become important parts of American culture and English culture. Such phrases as ace in the hole, ace up one's sleeve, beats me, blue chip, call one's bluff, cash in, high roller, pass the buck, poker face, stack up, up the ante, when the chips are down, wild card, and others are used in everyday conversation, even by those unaware of their origins at the poker table.

Modern tournament play became popular in American casinos after the World Series of Poker began, in 1970. Notable champions from these early WSOP tournaments include Johnny Moss, Amarillo Slim, and Doyle Brunson. It was also during that decade that the first serious strategy books appeared, notably Super/System by Doyle Brunson (ISBN 1580420818) and The Book of Tells by Mike Caro (ISBN 0897461002), followed later by The Theory of Poker by David Sklansky (ISBN 1880685000).

Poker’s popularity experienced an unprecedented spike in the first years of the twenty-first century, largely because of the introduction of online poker and the invention of the hole-card camera, which turned the game into a spectator sport. Viewers could now follow the action and drama of the game, and broadcasts of poker tournaments such as the World Series of Poker and the World Poker Tour brought in huge audiences for cable and satellite TV distributors. Because of the increasing coverage of poker events, poker pros are becoming more and more like celebrities, with poker fans all over the world entering into expensive tournaments for the chance to play with them. This increased camera exposure also brings about a new dimension to the poker pro's game—the realization that their actions may be aired later on TV.

Major poker tournament fields have grown dramatically because of the growing popularity of online satellite-qualifier tournaments where the prize is an entry into a major tournament. The 2003 and 2004 WSOP champions, Chris Moneymaker and Greg Raymer, respectively, won their seats to the main event by winning online satellites.