The story follows Jane Nichols (Heigl), a young woman in love with her boss George, but she does not have the courage to tell him. A notorious doormat, she has been a bridesmaid in 27 weddings, usually shouldering much of the responsibility for planning the weddings as well. We're introduced to Jane the same night she meets Kevin Doyle (Marsden), a cynical young man who covers weddings for the local paper (though Jane is unaware of this). He is intrigued by the fact that she seems to be in two different weddings on the same night. Through a bizarre set of circumstances, they share a taxi ride home. Jane accidentally leaves her planner/calendar behind. Kevin finds it and realizes her bridesmaid duties are a regular phenomenon.
Soon after, Jane's spoiled and vain younger sister Tess (played by Malin Akerman), comes home to visit. She meets and falls in love with George, despite the fact that they are complete opposites. Tess continually lies to George to convince him that they are soulmates, much to Jane's dismay. Meanwhile, Kevin has been using Jane's calendar to find her and continually hound her for a date. Unfortunately, he has an ulterior motive. He is planning to write a story on the "perpetual bridesmaid", a piece that he believes will further his career.
After a very short courtship, George proposes to Tess, who of course assumes that Jane will plan everything for their wedding to be held in several weeks. Jane's emotional state deteriorates rapidly, while Tess' diva behavior increases dramatically. On top of that, Jane learns Kevin is actually a wedding journalist who plans to cover George and Tess' wedding (though still unaware of the perpetual bridesmaid article he plans to write). Kevin eventually deduces that Jane is in love with George, and pushes her to stand up for herself and what she wants. At the same time he asks his editor to hold the article about Jane. He is beginning to realize that there's more to her than he first thought, and the article doesn't portray her in a flattering light. His editor says she'll hold the story, but unbeknownst to Kevin, goes back on her word and publishes it anyway.
While running an errand, Jane and Kevin get stuck overnight due to weather, and realize they have feelings for each other, which they act on. But the following morning, Jane sees the article. She's understandably humiliated, and leaves him. Tess is furious with her for allowing herself to be manipulated, which furthers her depression. But when Jane finds out that Tess has cut up their mother's wedding dress (which she had planned to wear to her own wedding), she comes to her senses and realizes that George needs to know the truth. At the rehearsal dinner that night, Jane gives Tess one more chance to come clean. She refuses, so Jane proceeds to humiliate Tess during her speech with a slideshow that vividly demonstrates the lies Tess has fed George. The wedding is called off.
Eventually the girls' father forces them to see each other and work out their differences. Tess learns that she needs to be less selfish and more compassionate before she deserves a guy like George. Jane realizes that Kevin was right, and she needs to learn to take care of others without completely ignoring herself. Later that evening George invites Jane to a charity event, as he needs a date. She meets him at the office, where she finally confesses her feelings for him. He kisses her, but they both realize they have zero chemistry. Jane realizes Kevin is actually the right guy for her, and she ends up with him instead.
This film shows examples of the following tropes:
- Armor-Piercing Question: After Jane reveals the truth about Tess at the rehearsal dinner and destroys the wedding, Casey, of all people, approaches her and asks why she did it. Jane tries to defend herself by saying that someone had to reveal the truth, but Casey points out that all Jane really did was vent every bit of frustration she's ever felt all at once in a public setting, and that if she had done the right thing, she would feel better. Then comes the question: "Do you feel better?" The answer is a very hard "no."
- Armor-Piercing Slap: One Played for Laughs from Casey to Jane when she's mooning over George. Later on, Jane herself gives one to Kevin after she finds out about the article.
- Atomic F-Bomb: Jane becomes so pissed off about the fact that Kevin sent her flowers instead of George that she leaves the party temporarily to scream one in the hallway.
- Anguished Declaration of Love: Jane couples George's with a "quitting my job" speech, then gives Kevin a real one minutes later.
- Bait-and-Switch: When it flashes forward to the present day, it shows Jane trying on a wedding dress and we're led to believe it's for her wedding day. However she gets a call and the camera pans out, showing she's actually being a wedding planner and bridesmaid and she was helping a friend find a dress that fits.
- Big Applesauce: Set in New York, with the wedding to be held in Central Park.
- Bitter Wedding Speech: Tess tasks Jane with giving her a maid of honor speech at the rehearsal dinner, complete with a slideshow. Though Jane does recite the speech that Tess wrote for her, she does so in an extremely sarcastic way, and pairs it with pictures that reveal all of the lies that Tess has been telling to win George over; it ends with the engagement being broken and the wedding called off.
- Blonde, Brunette, Redhead: Tess, Jane and Casey respectively. Each with typically associated personalities.
- Bouquet Toss: One of these gone wrong is how Kevin and Jane meet.
- Bridezilla: Tess. Oh God, Tess. It even gets mentioned by name in the article Kevin writes.Tess: Someone alert sky traffic because Bridezilla is on the loose!
- Brilliant, but Lazy: Casey. She's a free-spirited and lazy Hard-Drinking Party Girl who Really Gets Around, and yet in an easily-missed line, it's revealed that she's an accountant.
- Broken Pedestal: Jane is horrified to learn that the deeply cynical Kevin (using a pen name) is the one who writes the wedding articles she reads.Jane: It's like finding out my favorite love song was written about a sandwich...
- Buxom Is Better: Jane mentions an aunt used to joke about Jane having small breasts, which seems ridiculous now. What's even stranger is that it's Tess that brings this up, even though Jane is significantly bigger than her.
- Can't Live With Them, Can't Live Without Them: Part of Jane's speech to Kevin.
- Caught in the Rain: This is exactly how Jane and Kevin first hook up.
- Consummate Liar: Tess continuously lies and bullshits George about being a healthy-living, outdoorsy girl, much to Jane's chagrin. Naturally, this blows up in her face.
- Cynicism Catalyst: Kevin's cynicism regarding weddings is because he had his big fancy wedding planned, but then his bride left him for his roommate.
- Deadpan Snarker: Kevin.
Jane: Do you also go around telling small children that Santa Claus doesn't exist? 'Cause someone needs to blow that shit wide open.
- Also Jane.
- Defrosting Ice Queen: A gender-flipped version with Kevin. He's given up on the whole idea of weddings (see Cynicism Catalyst above) and spends the first third of the movie either making fun of Jane or secretly plotting to exploit her story for a major article. However, as time passes and he discovers how much Jane loves weddings, he slowly starts to fall for her and remember his own passions.
- Everyone Can See It: Everyone knows how Jane feels about George. Except George, who's completely Oblivious to Love.
- Exact Words: Tess, in full Bridezilla mode, writes the maid of honor speech she wants Jane to give at the rehearsal dinner for her, and tells her not to change a word. Sure enough, Jane delivers the exact speech that Tess wrote...but she pairs the lines with embarrassing photographs and reads the whole thing in a mocking way, which makes Tess look like a liar and complete fool.
- Extreme Doormat: Jane, of course.
- Foolish Sibling, Responsible Sibling: Jane is the elder, responsible sister and her younger sister Tess is Foolish.
- Fourth Date Marriage: Tess and George go from dating to engaged to wedding in an alarmingly short time.
- Jane and Kevin are a subverted example. They marry a year after they get engaged.
- Freudian Excuse: When Jane was a child, her cousin was in a panic because something went wrong with her wedding dress just before she had to walk down the aisle. Little Jane devised a solution, and her cousin not only praised her effusively, but even called her the wedding's hero. Jane herself explains that this was the moment that she realized she had a knack for wedding planning, and that she loved the joy her help could bring to others.
- Gentleman Adventurer: George is a well-done modern version of this.
- Giant Poofy Sleeves: Many of Jane's dresses have giant pouffy sleeves, like the southern belle dress and teal dress.
- The Glorious War of Sisterly Rivalry: Jane's Promotion to Parent averted this when they were young, but said war is declared and played straight during the movie's events.
- Goth: Gina, the secretary at Jane and Casey's job. Even her wedding is gothic.
- It's All About Me: Tess, especially when she becomes engaged to George and asks Jane for help on the wedding planning.
- I Did What I Had to Do: Jane's justification for publicly humiliating Tess. It's clear that even she doesn't buy this explanation and realizes there were other methods to achieve her goal.
- I Gave My Word: Jane claims that all twenty-seven of the brides she's helped over the years have promised to appear in her own wedding when the time comes...and sure enough, the final shot of the movie (when Jane is marrying Kevin) reveals every single one standing on a specially-built platform, each wearing the outfit that Jane herself wore in the corresponding ceremony.
- I Miss Mom/Missing Mom: Even though they were quite young when their mother passed away (Jane was eight and Tess was several years younger), her loss is implied to be a huge factor in Jane's personality, a cause of sadness in the family (especially for their father), and a significant contributor to several plot points.
- It's All Junk: After Jane decides to stop being such a doormat and wasting her life waiting for George, she throws out all twenty-seven of the outfits she's gathered over the years, in a metaphor for cleansing her life of her old habits.
- Humiliation Conga: The speech and slideshow Jane delivers at Tess and George's rehearsal dinner is one that Jane herself deliberately sets up for Tess: the pictures are not only extremely unflattering, they reveal all of the lies that Tess has told to win George over, in front of an entire hall full of people.
- Kimono Is Traditional: One of Jane's bridesmaids dresses is a purple kimono that she wore at traditional Japanese wedding.
- Love Triangle: Between Jane, George and Tess.
- Maybe Ever After: At Jane's wedding, Tess approaches George and reintroduces herself, and he smiles and asks her to sit next to him, implying that they may get back together after all.
- Meaningful Name: Jane is supposed to be your typical "plain Jane" type.
- A Minor Kidroduction: the movie starts with Jane and Tess at their first wedding as kids. They see the bride in the bathroom with her dress ripped, so Jane takes Tess's hair ribbon to fix it. The bride then asks Jane to hold her train, showing the first time with her fate as a bridesmaid.
- Moment Killer: Kevin. Jane's overreaction is what makes him realize she has feelings for George.
- Mondegreen: An excellent lampshading of this occurs after Kevin and Jane get wasted in a bar and both demonstrate that they have no idea what the real lyrics are to "Bennie and the Jets". But that doesn't stop them from singing and dancing to it anyway.
- Never Trust a Title: A very, very minor example. Technically speaking, Jane didn't wear twenty-seven dresses in twenty-seven weddings...for one, the men apparently wore dresses and the women wore tuxes. The bride in question is among the twenty-seven in the end, and sure enough, she's wearing a tux; the tux is also shown in Jane's montage of trying on her collection of wedding outfits. It's a minor point, though, and let's face it, "26 Dresses and 1 Tuxedo" just doesn't have the same ring to it.
- No Sparks: Jane and George.
- O.O.C. Is Serious Business: Once Jane's finished showing the humiliating slideshow of Tess at the rehearsal dinner and giving a mocking speech that exposes all of the lies Tess has told, Casey approaches and tells her that even she thinks this was wrong. It's even lampshaded: Casey points out that her "moral compass doesn't exactly point north," so if she has a problem with Jane's actions, they must be bad.
- Pair the Spares: Jane's loose friend Casey and Kevin's girl-crazy co-worker Trent are implied to hook up at the end.
- Pimped-Out Dress: Some of Jane's bridesmaid gowns, a few of them pimped to truly epic/horrific proportions.
- Plucky Comic Relief: Casey. She does give Jane some much needed advice more than once in the story, though.
- Promotion to Parent: Jane.
- Race for Your Love: Jane uses a taxi and jumps a boat ramp in high heels during her race to get to Kevin at the end of the movie.
- Rage Breaking Point: Jane's personality and upbringing are the reasons she can stay so calm throughout the whole movie, even when she's grinding her teeth to respond, but when she finds out that Tess cut up their deceased mother's wedding dress to make it more "modern" she finally cracks.
- Really Gets Around: Casey, unashamedly so.
- Sibling Triangle: Both Jane and her sister Tess are attracted to George and it only gets worse when Tess gets engaged to him. Lampshades by Kevin in a complaint.
- Sibling Yin-Yang: Jane is smart, responsible, and selfless, while Tess is irresponsible, selfish, and carefree.
- Test Kiss: Jane and George, after Jane finally confesses her feelings for him; they mutually decide there's no spark.
- Themed Wedding: As Jane showcases her many bridesmaid dresses to Kevin, one of them comes with a parasol. Jane explains that it was for a themed wedding.
- Unfortunate Implications: Invoked in-universe by Jane. George has an adopted Latino son named Pedro, and at one point, Tess pays him to clean her apartment for her. During the speech/slideshow at the rehearsal dinner, Jane uses the information and a picture of the deed in question to deliberately suggest that Tess is racist for exploiting a Latino person for cleaning services.
- Villain Ball: Held by Kevin's editor, of all people. After Kevin begins to realize that he's treated Jane badly in his "perpetual bridesmaid" article, he calls his editor and asks her to hold the piece for a week. She agrees...then goes behind his back and runs the story anyway. Absolutely no justification is ever given for this; as someone on the Headscratchers page points out, the entire thing ends up feeling like a highly-contrived way to create tension between Kevin and Jane. Furthermore—and also appearing on the Headscratchers page— publishing a story when an author has specifically requested it not appear opens the paper up to a big libel suit, something any editor worth their salt would know.
- Was It All a Lie?: Jane asks Kevin this after she sees his article about her. She doesn't believe him when he says "no".