Nick Marshall (MEL GIBSON) is a confident man's man, a testosterone-laced bachelor who has no problems charming or bedding the ladies of Chicago. He's also a hot-shot advertising executive who's so sure that he's going to get a big promotion that his airhead assistants, Eve (DELTA BURKE) and Margo (VALERIE PERRINE), have already opened the bubbly.
Unfortunately, his boss, Dan Wanamaker (ALAN ALDA), knows that the buying power in America has switched over to young women, so he's hired Darcy Maguire (HELEN HUNT), another ambitious ad veteran from a rival firm, for the position. Neither Nick nor his buddy, Morgan Farwell (MARK FEUERSTEIN), are pleased with this development, especially when Darcy gives them "homework" - to come up with campaign ideas for various women's products -- on her first day.
Nick has other problems beyond that. His ex-wife, Gigi (LAUREN HOLLY), has just remarried so their 15-year-old daughter, Alex (ASHLEY JOHNSON), will be staying with him for two weeks. She clearly isn't happy about that prospect as she views him more like a distant uncle rather than a father. To make matters worse, Nick's having a devil of a time convincing coffee shop employee Lola (MARISA TOMEI) to go out with him. Clearly, Nick doesn't know what women want.
Then one night, a freak accident suddenly leaves Nick with the ability to hear any woman's inner thoughts. Upset and overwhelmed by this sudden flood of personal information, Nick thinks he's going crazy, as does Morgan who urges him not to tell anyone else about this condition. After he visits his former marriage counselor (BETTE MIDLER) who tells him that if he knows what women want he could rule the world, however, he suddenly realizes he could use this gift to his advantage.
As such, he then sets out to read the thoughts of the various women in his life and use that information to figure out his teenage daughter, bed Lola and impress Dan with Darcy's ideas before she does. While doing so, however, he eventually realizes why women behave and think the way they do, and soon begins to change his way toward them.