Newly elected to Congress, former local television news reporter Evan Baxter leaves his hometown of Buffalo, New York, and later moves to the community of Prestige Crest, located in the fictional town of Huntsville, Virginia, where his congressional campaign officially declares that he will change the world. Evan prays to God to give him this opportunity. His wife, Joan, also prays that she, Evan, and their three sons will be closer together as a family. On his first day, Evan receives a letter from his greedy boss, Congressman Chuck Long, who provides him with a prime office and gives the opportunity to join him as the junior co-sponsor to his Citizens' Integration of Public Lands Act (CINPLAN) bill. Over the next several days, strange events in Evan's life occur: Eight vacant lots in Prestige Crest are purchased under his name, and ancient tools and gopher wood are delivered there, pairs of animals start following him around everywhere he goes, he begins to grow a beard uncontrollably, and the number 614 starts appearing in various forms throughout his daily routines.
Evan comes to realize that this number actually refers to verse 14 in chapter 6 of the Book of Genesis, where God instructs Noah to build an ark in preparation for a coming flood. Although Evan initially rejects this idea, God himself starts appearing to Evan and assures him that a flood will come and the only way he can change the world will be building the ark instead. Evan himself decides to start building the ark with the tools and materials provided, giving him an opportunity to get closer to his sons, although Joan sees this as a midlife crisis.
Although Evan still maintains his career in Congress, his appearance alienates his three staffers and the animals that follow him everywhere become disruptive. God reappears to Evan and provides him a robe, and later warns him the flood will likely come mid-day on September 22. When Evan dons the robe, he finds he is unable to wear any other clothes, the robe seemingly displacing anything else he wears. Outraged by Evan's slothful appearance, Long fires him and has his name removed from the Public Land Act bill. Believing that Evan has gone insane, Joan leaves him, causing Evan to continue building the ark alone. God disguises himself as a waiter and later speaks to Joan in a restaurant, assuring her that she should see this as an opportunity for the entire family to get closer to each other. Joan is inspired and finally returns with the children to help Evan finish building the ark to prepare for the flood.
On September 22, Evan's three staffers show him evidence that Long had planned to build Prestige Crest after damming off a nearby water source, but Long had cut many corners in building the dam. They suspect Long would do the same with the Public Land Act Bill. With the ark finally complete, the police try to destroy it with a wrecking ball, as it violates land codes. As animals begin to board the ark, and rain falls, Evan realizes that the flood will be a result of Long's dam failing. He warns the onlookers to get aboard the ark as the dam indeed fails, destroying all the homes of Prestige Crest. The ark rides the floods down the streets of Washington, D.C. and comes to a halt in front of the Capitol, interrupting the vote for the Public Land Act Bill. This results in Evan accusing Long of being responsible for cost-cutting leading to the dam's failure, leading to several other members of Congress voting against the bill.
Long is being investigated by Congress for profiteering, while all the animals returning to their natural habitats. Evan is finally reinstated in Congress, and all the changes imposed onto him by God are no longer remaining. Evan re-encounters God during his hike, and He states that Evan changed his world as he prayed for, being closer to his family through his one Act of Random Kindness (ARK).
Steve Carell as Evan Baxter, a former news reporter who is now a congressman
Morgan Freeman as God
Lauren Graham as Joan Baxter, Evan's wife
John Goodman as Congressman Chuck Long, a senior congressman
John Michael Higgins as Marty Stringer, Evan's chief of staff
Jimmy Bennett as Ryan Baxter, Evan and Joan's youngest son
Graham Phillips as Jordan Baxter, Evan and Joan's middle son
Johnny Simmons as Dylan Baxter, Evan and Joan's oldest son
Wanda Sykes as Rita Daniels, Evan's assistant
Jonah Hill as Eugene Tennanbaum, one of Evan's staffers
Molly Shannon as Eve Adams, the Baxters' real estate agent
Ed Helms as Ark Reporter
Rachael Harris as Ark Reporter
Brian Howe as Builder
Harve Presnell as Congressman Burrows
Madison Mason as Congressman Dodd
Bruce Gray as Congressman Hughes
Paul Collins as Congressman Stamp
Jim Doughan and Meagen Fay as Neighbors
Dean Norris as Officer Collins
Jon Stewart has a cameo appearance as himself
Catherine Bell as Susan Ortega (Uncredited)
Maile Flanagan as Mail Carrier
Lisa Arch and Simon Helberg as staffers
David Barrera as Ark reporters
Ruth Williamson as neighbor
Jim Doughan as neighbor
Michael Roper as Congressional Reporter
Emily Eby as Animal Wrangler
Bart the Bear 2 and Honey Bump as bears
a standalone sequel and spin-off of Bruce Almighty (2003)