The 2013 Nippon Professional Baseball season was the 64th season since the NPB was reorganized in 1950.
At the beginning of the 2013 NPB season, a new livelier ball was introduced in secret. This juiced up baseball allowed more home runs to be scored, leading to Tokyo Yakult Swallows outfielder Wladimir Balentien to break the 55 single season home run record set by Sadaharu Oh and later tied by Tuffy Rhodes and Alex Cabrera. This caused three-term NPB commissioner Ryozo Kato to resign, although he claimed to be unaware of the juiced baseballs.
Note: All of the games that are played in the first two rounds of the Climax Series are held at the higher seed's home stadium. The team with the higher regular-season standing also advances if the round ends in a tie.
The regular season league champions, the Tohoku Rakuten Golden Eagles (PL) and the Yomiuri Giants (CL), received byes to the championship round.
The regular season league champions, the Tohoku Rakuten Golden Eagles (PL) and the Yomiuri Giants (CL), received a one-game advantage.