The roots of the league can be traced back to the formation of the "Greater Japan Tokyo Baseball Club" (大日本東京野球倶楽部, Dai-Nippon Tōkyō Yakyū Kurabu) in 1934.

As is common in Asian baseball (and unlike North American leagues), teams are generally named after their corporate owners, such as Yomiuri and Softbank.

Following the 2024 season, the Yokohama DeNA BayStars, who defeated the Fukuoka SoftBank Hawks 4–2 in the 2024 Japan Series, are the reigning champions.

The season starts in late March or early April, and ends in October, with two or three all-star games in July.

This has led to four occasions where the Japan Series champion did not win their league's pennant that year, with those being the 2007 Chunichi Dragons, 2010 Chiba Lotte Marines, and the 2018 and 2019 Fukuoka SoftBank Hawks.

A raise in the salaries of players is often blamed, but from the start of the professional league, parent companies paid the difference as an advertisement.

The wave of players moving to Major League Baseball, which began with Hideo Nomo "retiring" from the Kintetsu Buffaloes, then signing with the Los Angeles Dodgers, has also added to the financial problems.

Attendance suffered as teams lost their most marketable players, while TV ratings declined as viewers tuned into broadcasts of Major League games.

According to historian Joseph Reaves, "The only minor drawbacks to the team's popularity in the States were their kanji characters and their cumbersome Japanese name.

To fill out the league, four new teams were formed: the Hiroshima Carp, the Kokutetsu Swallows, the Nishi Nippon Pirates, and the Taiyō Whales.

Four JBL teams formed the basis of the Pacific League: the Hankyu Braves, the Nankai Hawks, the Daiei Stars, and the Tokyu Flyers.

Matsutarō Shōriki, the Giants' owner, acted as NPB's unofficial commissioner and oversaw the first Japan Series, which featured the Mainichi Orions defeating the Shochiku Robins 4 games to 2.

After these various franchise developments, by the end of the 1950s, Nippon Professional Baseball had contracted from the initial allotment of 15 teams down to the current number of 12.

On September 1, 1964, Nankai Hawks' prospect Masanori Murakami became the first Japanese player to play in Major League Baseball[13] when he appeared on the mound for the San Francisco Giants; he returned to Japan in 1966.

[further explanation needed] Continuing their dominance from the JBL, the Yomiuri Giants won nine consecutive Japan Series championships from 1965 to 1973.

The Lions had a powerful lineup in this period, loaded with sluggers such as Koji Akiyama, Kazuhiro Kiyohara, and Orestes Destrade.

Their defense also benefited from the services of skilled players such as Hiromichi Ishige, Hatsuhiko Tsuji and catcher Tsutomu Ito.

Among the pitchers employed by the Lions in this period was "The Oriental Express" Taigen Kaku, Osamu Higashio, Kimiyasu Kudoh, Hisanobu Watanabe, and relievers Yoshitaka Katori and Tetsuya Shiozaki.

In 1995, star pitcher Hideo Nomo "retired" from the Kintetsu Buffaloes and signed with the Los Angeles Dodgers.

The strike arose from a dispute that took place between the owners of the 12 professional Japanese baseball teams and the players' union (which was led by popular Yakult Swallows player-manager Atsuya Furuta), concerning the merging of the Osaka Kintetsu Buffaloes and the Orix BlueWave.

The dispute received huge press coverage (which mostly favored Furuta and the players' union) and was dubbed one of the biggest events in the history of Japanese baseball.

The players decided to strike on September 18–19, 2004, when no progress was made in the negotiations, as there was insufficient time left in the season to hold discussions.

[24] The 2013 season featured a livelier baseball, which was secretly introduced into NPB, resulting in a marked increase in home runs league-wide.

Three-term NPB commissioner Ryōzō Katō was forced to resign over the scandal when the changed baseball was revealed.

[25] Former Prime Minister Shinzō Abe's ruling Liberal Democratic Party has proposed expanding NPB to 16 total teams by adding two expansion franchises in each of the country's top-tier professional baseball leagues.

[28] With the lifting of states of emergency over major Japanese cities, NPB announced that it would begin its regular season on 19 June behind closed doors.

[30] On 10 July, NPB began allowing a limited number of fans to attend games, with plans to further ease restrictions in the near future.

[32] For most of its history, NPB regulations imposed "gaijin waku", a limit on the number of non-Japanese people per team to two or three—including the manager and/or coaching staff.

Americans rank #4 (Tuffy Rhodes, 55) and #7 (Randy Bass, 54) on the list of most home runs in a season, and #2 in single-season RBI (Bobby Rose, 153).

The 2014 series also celebrated the 80th anniversary of the establishment of Japan's professional baseball by holding an exhibition game of a joint team of Hanshin Tigers and Yomiuri Giants against the MLB All-Stars at the Koshien Stadium on November 11, 2014.