Rodney (Michael Vartan) and Mike (Sean Astin) are two of the top salesmen at Treadline Tire Company. Despite their mean treatment of both the secretaries, led by Jane (Celia Weston), and annoying co-worker Kenny Castro (David Cross), the two are well liked by their boss Bob Ferrell (Robert Klein) and after a great win in softball (which concludes with Mike giving Castro a wedgie), the duo spend a wild night at a strip club with their boss.
The next day, Rodney and Mike come into work to learn that Mr. Ferrell has died of a heart attack. Due to his seniority in the company, Castro takes his place. Rather than fire them, which would result in the two of them getting generous severance packages, Castro decides to "demote" the two to secretaries. Rodney is assigned to the sadistic Earl Frank (Ron White) while Mike is paired with new executive Elizabeth Holland (Constance Zimmer), whom Castro has a very one-sided crush on. At home, Rodney ends up lying to his beautiful fiancee Jennifer (Sara Foster) and her demanding father JR (Patrick St. Esprit) that he has received a promotion at work.
Desperate to reclaim their old jobs, Rodney and Mike decide to befriend the other secretaries, who happen to hate the obnoxious Castro as much as they do. While the group seeks revenge on Castro, eventually trapping him in a bathroom flooding with toilet water, the duo also help their new co-workers with their personal lives. For example, they help the overweight Betty (Cleo King) lose weight, confront another office worker who had a one-night stand with Tina (Jill Bartlett) and help the new girl Olivia (Cathy Shim) figure out the perfect anniversary gift for her husband (which they claim is a blow job). They also help the ladies' softball team win the Secretaries' League title. While Rodney (with the help of Jane) tries to keep the unsuspecting Jennifer under the impression he's been promoted, the womanizing Mike starts falling for Elizabeth, who eventually takes him out bowling.
All the while, Castro acts excessively mean to Rodney, Mike and the secretaries, moves that eventually cause him to blow a deal with Reilly Auto Parts, a national chain that would make Treadline one of the top tire brands in the country. The final straw comes when Castro destroys the secretaries' break room. Led by Mike and Rodney, the secretaries storm outside and protest, eventually forming a union. Unfortunately for Rodney, his secret is revealed when Jennifer and JR catch him participating in the protest on the local news. Rodney's lies lead to Jennifer calling off their engagement.
The next day, a defeated Rodney goes to Castro begging for his old job back, but Castro reveals that there was never a chance of that. Rather, desperate to make up the loss of the Reilly deal to corporate, Castro reveals that he will lay off the newly unionized secretaries at the end of the month. Along with Mike and Jane (who always wanted to be a salesperson), Rodney meets up with the Reilly executives himself, and the trio successfully close the deal just as a furious Castro bursts into the room. He challenges them to a fight and is quickly knocked out by Mike.
Finally receiving his old job back thanks to the Reilly deal, Rodney goes to apologize to Jennifer. He ends up stripping naked in front of her entire street proclaiming his love for her, fulfilling a promise he made earlier in the film. As Jennifer begs him to stop, it's revealed that all the secretaries have talked to her, telling her all the good he's done. Jennifer tells the now naked Rodney how proud she is of him, and the two reconcile.
In the end, Rodney marries Jennifer, Mike begins officially dating Elizabeth, Jane has become a sales rep for Treadline and the secretaries now have a new and much improved break room. In addition, Rodney and Mike are now running the company (which leads to Rodney finally winning JR's approval). When asked what happened to Castro, the duo reveal that instead of firing him, they gave him a job in the advertising department. The film ends with Castro dressed up in an embarrassing tire costume, dancing for traffic.