Hancock is not your regular super hero with an unblemished personality record. Since he has saved so many lives, you would think the public would love to have him around to save the day. But not quite.

To get his missions done, Hancock has damaged so many buildings, roadways, trains, cars, causing huge collateral damage to just about everything that got in his way. His reckless methods of wrecking things to get the job done are what have sapped the public of their favour towards him. The last time he captured several criminals, it cost the city $9 million to fix the damages. The public has had enough of Hancock, and they want him to stop or go to another city. So Hancock is depressed and takes to drinking heavily.

Then one day, Hancock saves Ray Embrey (Jason Bateman), who is about to be run over by a train. Ray is a Public Relations executive, who wants to return Hancock's favour for having saved his life. Hence Ray makes it his mission to change Hancock's tarnished super-hero image and have the public cheering and rooting for him. How does Ray plans to achieve the impossible? What strained relationship develops between Hancock and Ray's wife? That is the rest of the story.