The movie opens with a panoramic view of Jellystone park. There are mountains, water, families picknicing. Then we see Yogi Bear (voiced by Dan Aykroyd) and Boo Boo (voiced by Justin Timberlake) as Yogi is preparing to use a contraption to steal a family's picnic basket. The contraption involves a pulley to which Boo Boo attaches Yogi, who then soars down hill and snatches the picnic basket, but it breaks and there's food everywhere, although he manages to eat a chip which he dips in dip in midair.
Ranger Jones (T.J. MIller) then reports to Ranger Smith (Tom Cavanagh), who is the head ranger, that a bear distrubance had been reported. Ranger Smith blows off his subordinate, tells him to go stack some maps. In his office, a documentary producer named Rachel (Anna Faris), requests permission to make a documentary about Yogi bear. Smith pretends not to know whom she is talking about, but Yogi then tries to steal Smith's lunchbox.
Meanwhile, the city in which the park is located is bankrupt. The Mayor (Andrew Daly) speaks with his servile toady, his chief of staff (Nathan Corddry) regarding his idea to sell the park. The go tell Ranger Smith that if the park doesn't get profitable by the end of the week, it will be rezoned agricultural and sold to loggers.
Rachel puts a camera in Boo Boo's bow tie.
Smith and Rachel develop a little romantic thing and come up with an idea to have a fireworks thing to celebrate the park's 100th anniversary. The mayor tells Ranger Jones that if he messes up the celebration, he'll get promoted to head ranger. When he finds out that it took Ranger Smith 12 years to make head ranger, he tells yogi to show off for the park goers.
Suddenly, the park is flooded with visitors on the day of the celebration. And Boo Boo pulls Yogi on water skis from a row boat with a small horsepower engine. Yogi, showing off, loses control and crashes into the fireworks stand in the water which causes all the fireworks to go off, some headed towards the viewers.
Having failed to sell enough season passes from the celebration, the park is sold and the Mayor plans to hold a press conference in the park to celebrate saving the city's budget. Yogi and boo boo have to resort to acting like actual average bears and forage for food, which does not go well.
Rachel and Ranger Smith realize that Yogi's pet turtle was an endangered "frog mouth turtle."
Ranger Jones has a change of heart and helps Ranger Smith, Yogi, Boo Boo, and Rachel as they try to save the day by calling the media's attention to the turtle. After a chase scene, they catch the Mayor on Boo Boo's camera saying damaging things and shove the clip into the mayor's video that he is showing at the press conference.
The park is saved and it lives on happily ever after.