Little League Baseball: Championship Series is part of the SNK Playmore series of Baseball games for the NES. It features very similar gameplay to its predecessor Baseball Stars. The players are modeled after Little League-aged kids and the game features Little League rules (six innings, ten run rule, no leading off a base, no stealing until the pitch had crossed the plate, etc.). Sixteen teams from three different continents feature in the game.
The game is heavily based on SNK's 1989 NES game Koushien, which is based on a baseball tournament in Japan for highschool-aged athletes that culminates at Koushien stadium. Little League Baseball is essentially to Koushien what R.B.I. Baseball is to Konami's Family Stadium: structurally similar, but for some major graphical and localization-related changes necessitated by the differences between the two markets.
Unlike actual Little League rules, the tournament is a single elimination that features all sixteen teams. As the player's team progresses through the tournament they are presented with a password that could be entered to continue at a later time. All 16 teams can be human controlled. No accumulated stats are kept in this mode. Games that had two computer-controlled teams can either be watched in full, or put in 'Speed Mode' where the game's result was immediately simulated and shown on the scoreboard.
A single game that can be played between a human and the computer, two human players, or a computer vs. computer game could be watched.
Each team in Little League: Championship Series has an overall team stat in four categories: Batting, Running, Pitching and Defense. In Power Analysis, the player can see all of the teams' overall stats.
Sixteen teams from three different continents feature in the game. Stats are out of a possible maximum of 5. New York has the highest overall rating with 19 out of a possible 20. Italy has the lowest with 8.