The origins of the card game of Poker are somewhat disputed, but most game historians believe that its present day form is derived from the elements of several games.

The name Poker probably comes from an eighteenth-century French game called Poque. Some historians believe, however, that the name is also derived from a German betting game, Pochspiel, which contains an element of bluffing. In pochspiel, players would indicate whether they wanted to pass or open by rapping on the table and saying, "Ich Poche!" Also mentioned as a possible source for Poker's name is the Hindu word, pukka.

Another possible explanation for the word Poker is that it came from a version of an underworld slang word, "poke," a term used by pickpockets. Cardsharps who organized card games to relieve a sucker from his poke (cash and valuables) may have used that word among themselves, adding an r to make it "poker." There are those who also believe that "poke" probably came from "hocus-pocus," a term widely used by magicians.

One of the likely ancestors of the game of Poker was the Persian game of As Nas, which was a 5-player betting game using a deck of 25 cards with 5 suits. The 16th-century gambling card game called Primero was popular in Europe and has many similarities to modern day Poker. The French game of Brelan and its derivative, the English game Brag (earlier spelled Bragg), both incorporated the element of bluffing, but this concept was known in other games as well.

The earliest references to a game called Poker were by English actor Joseph Cromwell, who described a card game being played in New Orleans in 1829, and Jonathan H. Green, who made a written reference to Poker in his book, An Exposure of the Arts and Miseries of Gambling (1843). In his writing, Green mentions rules to what he called the "cheating game," which was then being played on Mississippi riverboats. Some historians say Green was the first to refer to this "cheating game" by the name Poker.

These early descriptions mention a game played with a deck of 20 cards, in which four players bet on which player's hand was the most valuable. As the game spread into the rest of America, heading west with the California Gold Rush, it adopted the full 52-card English deck. The flush was introduced, and other additions were made during the American Civil War, 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.

Prior to the 1970s, Poker was not found at many casinos because of the difficulty of keeping out cheaters. In the 1980s and 90s casinos were in the habit of closing down Poker rooms in favor of blackjack and roulette. Better security techniques, heavy promotion and tournament play brought renewed interest in the game.