The film opens with Yogi Bear (Dan Aykroyd) and Boo Boo (Justin Timberlake) using a zip line to swoop by an unsuspecting family and stealing their picnic basket. We cut to Ranger Smith (Tom Cavanagh) and Ranger Jones (T.J. Miller) hearing about the incident with Yogi and Boo Boo so Ranger Smith decides to check it out. He finds Yogi and Boo Boo trying to steal another picnic basket but their plan fails and Yogi gets hit in the face with a pie. Ranger Smith yells at the bears and tells them they shouldn’t be stealing picnic baskets anymore and that they should be hunting their own food.
We then cut to Mayor Brown (Andrew Daly) and his Chief of Staff (Nathan Corddry) talking about how the town is running out of money. They need to find a part of the government that is losing a lot of money to shut down. Unfortunately, that just happens to be Jellystone Park. Mayor Brown goes down to Jellystone to visit Ranger Smith and tells him that if they do not raise enough money, Jellystone will be shut down. Rachel (Anna Farris) then comes by and asks Ranger Smith if she could shoot a documentary in Jellystone. He agrees and soon after she runs into Yogi and Boo Boo. They agree to put a camera on Boo Boo’s bow so she can see everything.
Yogi and Boo Boo return to their cave to find Ranger Smith coming by for a visit. Ranger Smith sees Yogi’s new invention, the Picnic Snatcher 2000, which he then confiscates. He then tells them about the closing of Jellystone. That night, Ranger Smith is has dinner with Rachel. They are having a good time until they are interrupted by Yogi and Boo Boo who have raised about a hundred dollars in cash. When Ranger Smith asks Yogi where he got the money, he says he took it from the brown box at the front gate. Ranger Smith tells him that is where people pay to park. Yogi tells Ranger Smith about his idea for a fireworks show to raise even more money.
The next day, they put up flyers and advertisements all over town for Jellystone’s big fireworks show. Mayor Brown is worried that this plan might actually work and he won’t be able to close down the park so he tells Ranger Jones to ruin the fireworks show somehow and then he will make him the head ranger of Jellystone. Ranger Smith tells Yogi and Boo Boo to stay away from the show in order to keep them from ruining things for Jellystone. Ranger Jones secretly tells Yogi to come to the show and do his own act, in order to sabotage the show. Yogi does a water skiing act at the show but messes up and lights himself on fire and hits the pile of fireworks nearby. The fireworks go off on the crowd and puts everyone in danger, including almost killing Ranger Smith and Rachel.
Because of the fireworks disaster, Mayor Brown closes down Jellystone and Ranger Smith is reassigned to a park that’s the size of three cars. Yogi, ashamed of his role in the closing of the park, leaves Boo Boo to go live on his own where he can do no more harm. Boo Boo later finds him and convinces him to find Ranger Smith and to find a way to get Jellystone re-opened. They hop a train and arrive at the tiny park and convince him that they should try to get Jellystone reopened. Back at Jellystone, Ranger Jones comes to the realization that Mayor Brown and his Chief of Staff have been plotting to cut down all the trees in order to make money.
Yogi, Boo Boo, and Ranger Smith meet up with Rachel who has discovered the last Frog-Nosed Turtle in the world in Yogi’s cave. It turns out that it is Boo Boo’s pet and she found it through Boo Boo’s bowtie camera which is still in the cave. Since the Frog-Nosed Turtle is an endangered species, then they can save Jellystone from being cut down. They can’t get into the park because of Mayor Brown but Ranger Smith finds a hidden gateway since he knows the park so well.
The Chief of Staff finds out about the Frog-Nosed Turtle and sends Ranger Jones to get it. Ranger Smith realizes that they need the picnic Snatcher 2000 in order to catch the Frog-Nosed Turtle from the Mayor and so he gets Yogi and Boo Boo to steal it and the Frog-Nosed Turtle. Yogi and Boo Boo skydive from a plane and are able to successfully steal it thanks to a diversion from Ranger Jones. They crash and escape in a life boat with the frog in tow.
Yogi and Boo Boo find Ranger Smith and Rachel and grab them onto the life boat. The boat rushes down and crashes through the rapids and down the waterfall. Mayor Brown is about to make a big speech that will officially start the demolishment of Jellystone and they all realize that they have no chance of getting there in time. That’s when all of a sudden Ranger Jones comes in with the car that Ranger Smith would not let him drive before. He is against the destruction of Jellystone and decides to help Yogi and the gang.
They make it to the big speech before it starts but the Chief of Staff steals the Frog-Nosed Turtle away from them. The Frog-nosed Turtle escapes from him. Ranger Smith then plugs Boo Boo’s camera tie into the projector and it shows on the big screen in front of the crowd Mayor Brown confronting Yogi and his friends about his true evil plans. He then claims to the crowd that there is no Frog-Nosed Turtle but it then pops up next to him. Now that everyone knows about it, Jellystone Park is now saved.
They reopen Jellystone and Ranger Smith and Rachel become a couple. Ranger Jones goes back to being an assistant and he is happy with that. The film ends with Yogi and Boo Boo going back to their old tricks. They tie one end of a string to a picnic table and the other end to a tractor. When the families come to eat with their picnic food, they drive off with all of the food with Ranger Smith, Rachel, and Ranger Jones chasing them.
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