Harlow plays Lilian "Lil" Andrews, a red-headed secretary who, as the film opens, is scheming to seduce her boss, Bill Legendre. She eventually succeeds, breaking up Bill's marriage and marrying him herself, but when an even richer man, coal magnate Charles B. Gaerste, arrives in town, Lil sets her sights even higher.
Harlow, who usually appeared as a platinum blonde, dyed her hair red for this role. This was probably the height of her sexiness in the Pre-Code Era; after The Hays Code started getting enforced MGM toned it down and Harlow started playing more all-American types. Red-Headed Woman was a Star-Making Role for Charles Boyer, who appears as the French chauffeur who is sleeping with Lil while Lil is setting her sights on Gaerste.
- Deadpan Snarker: Lil's best friend and roommate, Sally.
- Distracted by the Sexy: Bill can't concentrate on the memo he's trying to dictate when Lil is showing off her legs.
- Drowning My Sorrows: Lil gets drunk after Bill doesn't show up at her apartment for a scheduled rendezvous.
- Establishing Character Moment: In the first shot, Lil is getting her hair dyed red. She gleefully cackles "So gentlemen prefer blondes, do they?" In the next shot, she's trying on a dress. She asks if it's see-through, and when the saleslady says "I'm afraid it is", Lil says "I'll wear it!"
- Evil Redhead / Villain Protagonist: Harlow is so charismatic that one is tempted to root for Lil, but she's a gold-digging homewrecker without any conscience.
- Fanservice: An incredible moment in which Harlow is briefly shown topless while changing underwear. It's a very quick shot, but still quite obvious.
- Fiery Redhead: Lil. If you dump her, she may just pull out a gun and try to shoot you. She may also crash your ex-wife's party and make a scene, or barge into your home while you're trying to make up with the wife.
- Foot Popping: Lil and her bootlegger boyfriend go behind the cupboard in a bar, so we only see their feet. She then lifts one of their legs, showing that they're kissing.
- Gold Digger: So much so that when an even richer man pops up as a target of opportunity, Lil decides to abandon her wealthy husband.
- Hit Me, Dammit!: After Lil taunts Bill, saying that he's afraid to be alone with her because he's attracted to her, Bill slaps her. She smiles broadly and says "Oh, do it again, I like it!"
- In-Series Nickname: Lilian is called "Lil" by most people. Bill sometimes calls her "Red."
- Karma Houdini: Lil is eventually dumped by both Bill and Charles, but she escapes punishment for shooting Bill, and the film ends with her in France as the Trophy Wife of some rich French guy (and it's implied that she's having an affair with his chauffeur).
- Really Gets Around: Lil. She uses sex to get ahead in society, but she also enjoys it. While seducing Gaerste, she also has an affair with his chauffeur, Albert.
- Sexy Backless Outfit: Lil wears one for the party that she hosts.
- Shout-Out: The first line in the film is Lil saying "So gentlemen prefer blondes, do they?" The screenplay was written by Anita Loos, who wrote Gentlemen Prefer Blondes.
- Stocking Filler: When Lil is seducing Bill, she shows him that he put a small picture of him to her garter. Later, when he wants to break up with her, she shows her stockings again to prove that she's removed the picture.
- Title Drop: A nightclub crooner sings a song called "Red-Headed Woman".
- The Vamp: Lil shamelessly exploits her sexuality to seduce men and gain social status.
- Victoria's Secret Compartment: Where Lil puts the key after locking herself and Bill in her bedroom.
- Your Cheating Heart: Lil seduces the married Bill. Later, she cheats on him with Gearste, and cheats on Gearste with his chauffeur.