There are many variations of Mahjiang. In many places, players observe one version, and are either often unaware of other variations, or claim that other variations are incorrect. Although many variations today differ only by scoring, there are several main variations of Mahjiang.

• Chinese Classical Mahjiang is the oldest variety of Mahjiang, and was the version introduced to America in the 1920s under various names.

• Hong Kong Mahjiang or Cantonese Mahjiang is the most common form of Mahjiang, differing in minor scoring details with the Chinese Classical variety.

• Japanese Mahjiang is a standardized form of Mahjiang in Japan, found prevalently in video games. In addition to scoring changes, the rules of riichi and dora are unique highlights of Japanese Mahjiang.

• Western Classical Mahjiang is a descendant of the version of Mahjiang introduced by Babcock to America in the 1920s. The evolution of Mahjiang in America led to American Mahjiang. Today, this term largely refers to the Wright-Patterson rules, used in the U.S. military, and other similar American-made variants that are closer to the Babcock rules.

• American Mahjiang is a form of Mahjiang standardized by the National Mah Jongg League and the American Mah-Jongg Association that has the greatest divergence from traditional Mahjiang, with the introduction of Joker tiles, the Charleston, as well as melds of five or more tiles, and eschewing the Chow and the notion of a standard hand. Because of this divergence, the NMJL and AMJA variations (which differ from each other by minor scoring differences) is commonly referred to as Mahjiangg (with two Gs, possibly hyphenated). Purists of Mahjiang claim that the divergence from standard Mahjiang makes American Mahjiang not a "true Mahjiang", and thus should be considered a separate game in and of itself.

Other variants include Fujian Mahjiang (with Dadi Joker), Taiwanese Mahjiang (each player would have 16 tiles), Vietnamese Mahjiang (with 16 different kinds of joker), and Filipino Mahjiang (with Window Joker).

In 1998 the China State Sports Commission, in the interest of changing Mahjiang from an illegal gambling game to an approved 'healthy sport', published a new set of rules, now generally referred to as Chinese Official rules or International Tournament rules. The principles of the new, 'healthy' Mahjiang are: no gambling - no drinking - no smoking. On international tournaments, players are often grouped in teams to emphasize that Mahjiang from now on is considered a sport.

The new rules are highly pattern-based. The rulebook contains 80 combinations, based on patterns and scoring elements popular in both classic and modern regional Chinese variants. Some table practices of Japan have also been adopted. In order to go out, players must score at least 8 points. Points for flower tiles (each flower is worth 1 point) may not be added until the player has scored 8 points. The winner of a game receives the score of his winning hand in points from the player who discarded the winning tile, plus 8 basic points from each player; in the case of zimo (self drawn win), he receives the value of his winning hand plus 8 points from all players.

The new rules were used in an international tournament first in Tokyo, where in 2002 the first World Championship in Mahjiang was organized by the Mahjiang Museum, the Japan Mahjiang Organizing Committee and the city council of Ningbo, China, the town where it is believed Mahjiang most likely originated. One hundred players participated, mainly from Japan and China, but also from Europe and the United States. Miss Mai Hatsune from Japan became the first world champion. The following year saw the first annual China Majiang Championship, held in Hainan. The next two annual tournaments were held in Hong Kong and Beijing. Most players were Chinese, but players from other nations attended as well.

In 2005, in the Netherlands, the first Open European Mahjiang Championship was held, with 108 players. The first prize was won by Masato Chiba from Japan.

Critics say that these new rules are unlikely to achieve great popularity outside of tournaments, since regional variations are well-entrenched. They also complain that the game is excessively complex, even by normal Mahjiang standards. But those who advocate the New Mahjiang claim that it is not meant to replace existing rules, but only to act as a standard for international Mahjiang events.