Holly Berenson (Katherine Heigl) is the owner of a small Atlanta bakery and Eric Messer (Josh Duhamel), known as Messer, is a promising television technical sports director for the Atlanta Hawks. After a disastrous first date set up by their best friends (Peter and Alison), all they have in common are their mutual dislike and their love for their shared goddaughter, Sophie Christina Novak.



However, after a devastating car accident which kills both Peter and Alison, they are left as the one-year-old Sophie's legal guardians. They try to put their differences aside, since they are advised to both move into Sophie's home in order to minimize her need for adjustment to the new situation. They struggle to learn how to care for Sophie and to get along with each other. This goes on and once Holly leaves Sophie with Messer while she covers an important catering job - the same night that he is given the opportunity to direct a big basketball game. When Messer loses his focus due to Sophie's constant crying, he returns home to argue with Holly and leave on his motorcycle. Later, he comes back and makes amends with Holly. Holly attends a date with a doctor named Sam (Josh Lucas) (whom Messer nicknames "Doctor Love") who is also Sophie's pediatrician. This date is cut short when Messer calls and explains Sophie is unwell. Later, Messer sees Holly kissing Sam. Life goes on till they see the monthly bills and realize it's way more than they expected. Holly then admits to Messer that because of finance at home she can't afford the extension on her catering business, so Messer offers to give her the money.



She refuses to take it so Messer offers it as an investment, to which Holly accepts. The pair agree to go on a date to celebrate, and when they return to the house they end up having sex together. Messer is offered a director job in Phoenix, Arizona with the Phoenix Suns. Since this has been his career goal for several years, he seriously considers making the move, but does not discuss it with Holly. When Holly learns of the proposed move at a neighborhood block party, she is upset and orders him to go to Phoenix.



At Thanksgiving, Messer returns to Atlanta hoping to patch things up with Holly but finds her in a relationship with "Doctor Love." He and Holly exchange heated words in the kitchen before he tells her he loves her, and always has. After Holly instructs him to do so, Messer leaves for the airport.



That evening, Sam tells Holly that if he and his ex-wife argued like that they'd still be together now, and with that he leaves. When their Child Protective Services caseworker shows up for the last appointment to see if Holly and Messer are fit parents for Sophie, Holly realizes that she can't take care of Sophie without him and drives to the airport with the caseworker. Holly finds that the flight has departed and returns to the house disappointed where, to her surprise, she finds Messer. They kiss and the film ends with them still together as a family on Sophie's second birthday, with a two year cake to celebrate the infant's birthday.