Abby Richter (Katherine Heigl) is a morning show TV producer in Sacramento, California. Abby firmly believes in true love and is a big supporter of complex self-help books such as Chicken Soup for the Soul and Men Are from Mars, Women Are from Venus. Coming home from a disastrous date, she happens to see a segment of a local television show, The Ugly Truth, featuring Mike Chadway (Gerard Butler), whose cynicism about relationships prompts Abby to call in to argue with him on-air. The next day, she discovers the TV station is threatening to cancel her show because of its poor ratings. The station owner has hired Mike to do a segment on her show.
At first, the two have a rocky relationship; Abby thinks Mike is crass and disgusting while Mike finds her to be naive and a control freak. Nevertheless, when she meets the man of her dreams, a doctor named Colin (Eric Winter) living next to her, Mike convinces her that by following his advice she will improve her chances with Colin. Abby is skeptical, but they make a deal: If Mike's management of her courtship results in her landing Colin, proving his theories on relationships, she will work happily with him, but if Mike fails, he agrees to leave her show.
Mike succeeds in improving the ratings, brings married co-anchors Georgia and Larry closer and successfully instructs Abby to be exactly what Colin would want through a number of pointers including: always laugh at his jokes and say he is amazing in bed. Mike is invited to appear on The Late Late Show with Craig Ferguson and is offered a job at another network. Abby is forced to cancel a romantic weekend away with Colin, during which they had planned to finally sleep together, and instead fly to Los Angeles to persuade Mike to stay with her show.
They drink and dance and Mike admits he does not want to move because he wants to stay in Sacramento near his sister and nephew. In the hotel elevator, they passionately kiss, but go to their separate rooms. Mike, dealing with the intensity of his feelings for Abby, calls on her room only to find Colin has shown up to surprise her. Mike leaves. Abby is upset and soon realizes Colin only likes the woman she has been pretending to be, not the real her. She breaks up with him.
Mike quits and takes a job with a rival TV station in Sacramento, and ends up doing a broadcast at the same hot air balloon festival as Abby. He cannot resist intruding when she kicks the new "Mike Chadway" imitator off the air and goes into a tirade about what cowardly weaklings men are. The balloon takes off while they argue. Abby says she broke up with Colin, and Mike admits he loves her. Abby kisses him while they fly off, all of which is broadcast due to a camera mounted in the balloon. The film ends with Abby and Mike in bed. When Mike asks if she was faking it, Abby smirks and responds, "You'll never know.