Mark Ruffalo filmed his role in only six days.

Julianne Moore received the script, and agreed to star in the film five years before filming began.

Filmed in twenty-three days, because the creators had rushed post-production, so it would be finished in time for Sundance. Even though it was admitted after the deadline, the movie became one of the breakout hits of the festival.

Ewan McGregor was originally cast to play Paul.

The film's title is based on the title of the song "The Kids Are Alright" by The Who.

Jules (Julianne Moore) has a tattoo on her left wrist that reads "JLN". This stands either for "Jules Loves Nic" or "Joni Laser Nic". The ink can most easily be seen about twenty minutes into the film when Jules and Nic are watching Locked Up Abroad (2007).

Much of the film is based upon co-Writer and Director Lisa Cholodenko's relationship with her partner Wendy, who both had a son by a sperm donor. Cholodenko dedicated the film to them.

Annette Bening's favorite scene, is when Jules (Julianne Moore) and Nic (Annette Benning) are telling Paul (Mark Ruffalo) how they first met, and watching Joni (Mia Wasikowska) and Laser (Josh Hutcherson) cringe at the erotic details.

Features children of Steven Spielberg and Kate Capshaw, Michael Eisner, and Lindsay Crouse and David Mamet.

Paul's restaurant is named WYSIWYG, a common abbreviation for "What you see is what you get", which is perhaps a commentary on his character.

Robin Wright was previously considered for the role of Nic.

The Elvis Costello t-shirt Julianne Moore is wearing, belonged to Lisa Cholodenko.

Annette Bening and Julianne Moore were nominated for the Best Actress Oscar in 1999. Bening was nominated for American Beauty (1999), while Moore was nominated for The End of the Affair (1999). They both lost to Hilary Swank for Boys Don't Cry (1999).

Although this movie only played in seven theaters during its first weekend of North American release (three in New York City and one each in San Francisco, Chicago, Toronto, and Los Angeles), in terms of per-screen average, it was the box-office winner for the weekend.

When Jules is trying, awkwardly, to explain the reasons that lesbians might prefer to watch gay male pornography rather than porn showing two women together, one of the reasons she gives is that they always cast two straight women pretending to be gay in those movies. Both Julianne Moore, who plays Jules, and Annette Bening, who plays Nic, are, in their real-lives, straight actresses pretending to be lesbians, for this movie.

Over the years that the film was in pre-production, Evan Rachel Wood, Robin Wright, and Ewan McGregor were attached for roles.

Annette Bening and Mia Wasikowska both shared the same stand-in.

The film was greenlit for 2006, but Lisa Cholodenko postponed the project when she became pregnant.

This film is Julianne Moore's second time playing a lesbian character. The first portrayal was of Lila Crane in Psycho (1998).

Julianne Moore would reunite with Josh Hutcherson to star in The Hunger Games: Mockingjay - Part I (2014) and The Hunger Games: Mockingjay - Part 2 (2015).

In her bedroom, Joni has a poster of Uh-Huh-Her, the group of actress Leisha Hailey (who is openly gay).

The film has four references to wineries that appear prominently in Sideways (2004). During the first family dinner scene, the label of the wine bottle on the table is Frass Canyon; Nic looks at it and asks Jules if there is any more Fiddlehead. Frass Canyon is the contrived name of the winery where Paul Giamatti's character in Sideways (Miles) drinks from the spittoon and then dumps the remaining liquid on his head. Miles and Virginia Madsen's character in Sideways (Maya) rave about the Fiddlehead Sauvignon Blanc that Maya is drinking when the two couples meet for dinner--immediately following the famous Merlot scene. When Paul visits Jules and Nic's home for the first time, he announces that he's brought a bottle of Petite Sirah; the label is from Kalyra, the winery where Sandra Oh's character in Sideways works and meets Jack (Thomas Haden Church). Just before the scene when Nic learns of Jules's affair, Paul excitedly tells Nic that he has a "killer" bottle of Alma Rosa Pinot Noir (and the Alma Rosa label appears on the bottle). Alma Rosa is the winery owned by Richard Sanford. At the time Sideways was filmed, Richard Sanford owned Sanford, the first winery stop for Miles and Jack where Miles waxes poetic about Sanford's Pinot Noir. Alma Rosa's tasting room was the Sanford tasting room that appeared in Sideways, and Chris Burroughs, the wine pourer at Sanford in the film, poured for Alma Rosa as recently as 2014.

Second collaboration between Julianne Moore and Mark Ruffalo, following Blindness (2008).

Many of the characters in the film are seen wearing "Free City" clothing. "Free City" was created by Nina Garduno, girlfriend of Leisha Hailey.

Annette Bening had previously replaced Julianne Moore when she dropped out of the role of Deirdre Burroughs in Ryan Murphy's Running with Scissors (2006).

The only film that year to be nominated for Best Picture at the Academy Awards, but not at the Critics' Choice Movie Awards.