On October 25, 1986, the Boston Red Sox faced the New York Mets in game 6 of the World Series. Boston led the best-of-7 series 3 games to 2, and had a two-run lead with two outs in the bottom of the tenth inning. New York came back to tie the game with three straight singles off Calvin Schiraldi and a wild pitch by pitcher Bob Stanley. Mookie Wilson fouled off several pitches before hitting a ground ball to Buckner at first base. The ball bounced on the dirt and rolled under Buckner's glove, through his legs, and into right field, allowing Ray Knight to score the winning run from second base, forcing a seventh game, which the Mets won two nights later.

Buckner's error capped off a very poor overall Game 6 performance for the first baseman; he went 0-for-5 with runners on in all five at-bats in that game, the only player to do so until the Yankees' Hideki Matsui in the 2005 ALDS.

Buckner has denied any lingering bitterness over the 1986 Series fiasco, pointing out that he was a key member of the team that year. He hit 8 home runs that September, with 22 RBIs and a .340 average, missing only three games. He drove in over 100 runs for the season. In game 5 of the Championship Series when the Red Sox faced elimination, he singled to start their ninth inning rally capped off by Dave Henderson's famous home run.