Overview
Interleague play, introduced in 2005, features official games between Central and Pacific League teams. Since 2015, each team plays 3 games against all 6 opponents from the other league for a total of 18 interleague games (reduced from the original 36-game format to balance the overall season schedule). The Pacific League has maintained a cumulative winning record since inception, reinforcing the 'stronger Pacific' narrative that dominates annual discussions. SoftBank Hawks have been particularly dominant, claiming multiple interleague championships. The DH rule applies in Pacific League home games but not in Central League venues, following the home team's league rules. For players, facing unfamiliar pitchers and hitters from the other league provides a fresh challenge, while fans enjoy a preview of potential Japan Series matchups. Interleague results count toward the regular season standings, making them a significant factor in pennant race outcomes.
How the Number of Interleague Games Has Changed
The number of interleague games each club plays has been reduced twice since the format began.
| Period | Games | Format |
|---|---|---|
| 2005-2006 | 36 games | A three-game home series and a three-game road series against each of the six clubs in the other league |
| 2007-2014 | 24 games | Cut to two games at home and two on the road against each club |
| 2015 onward | 18 games | A single three-game series per matchup, with home hosting rights alternating year by year |
The reductions were driven by the need to balance interleague games against intraleague games and to keep the calendar manageable. Because the 18-game format pairs each club either at home or on the road but not both, a given opponent now visits any particular ballpark only once every two years.
Historical Results and the Case for the 'Stronger Pacific'
Cumulative interleague results favour the Pacific League by a wide margin: through the end of the 2026 interleague schedule the Pacific led 1,434-1,256 with 82 ties. Season by season, the Pacific has finished ahead 18 times against just 3 for the Central (2009, 2021 and 2022). Pacific clubs have also taken the interleague title 16 times to the Central's 5, with SoftBank alone accounting for 9. These lopsided figures are the single strongest piece of evidence behind the phrase 'the Pacific has the talent', and every year they reopen the debate over what causes the gap - the division of labour between pitchers and hitters that the DH creates, differences in player-development systems, and more.
Frequently Asked Questions
Q. When did interleague play begin?
In 2005. It was introduced as official competition across league lines in the wake of the 2004 franchise-realignment crisis.
Q. How many interleague games does each team play?
18 since 2015 - three games against each of the six clubs in the other league. The original 2005-2006 format called for 36 games, and from 2007 to 2014 it was 24.