Written by frontman Rivers Cuomo, the song came to be after he had all the music finished and one line, "Say it ain't so".

[1] Cuomo made a connection to an incident in high school where he came home and saw a bottle of beer in the fridge.

[4] In 2008, Rolling Stone ranked "Say It Ain't So" number 72 on their list of "The 100 Greatest Guitar Songs of All Time.

"[10] The music video for "Say It Ain't So", directed by Sophie Muller, met with less success than the previous two Weezer videos directed by Spike Jonze, but the song still successfully climbed to the top 10 of the Modern Rock Tracks chart.

[26] "Say It Ain't So" is a playable track in the video games Rock Band[27] and Rocksmith 2014[28] in addition to appearing on an episode of Hindsight.