At the conclusion of the regular season, all five playoff positions were undecided going into the final day of the schedule.

[1] The NC Dinos became the first defending champion to miss the playoffs since the Kia Tigers in 2010,[2] while the Doosan Bears qualified for the seventh consecutive year.

2021 also marked the first KBO season for the SSG Landers, formerly known as the SK Wyverns.

Games are declared ties after 12 innings (15 in the postseason), and those contests have no bearing on a team’s winning percentage.

[3] *Samsung Lions hosted tiebreaker game by virtue of head-to-head record with KT Wiz (9-6-1) **KT Wiz won against Samsung Lions 1-0 in the tiebreaker game The series started with a 1–0 advantage for the fourth-placed team.