A young Peruvian bear with a passion for all things British travels to London in search of a home. Finding himself lost and alone at Paddington Station, he begins to realize that city life is not all he had imagined - until he meets the kind Brown family, who read the label around his neck ('Please look after this bear. Thank you.') and offer him a temporary haven. It looks as though his luck has changed until this rarest of bears catches the eye of a museum taxidermist.
A young Peruvian bear travels to London in search of a home. Finding himself lost and alone at Paddington Station, he meets the kindly Brown family, who offer him a temporary haven.
- An explorer named Montgomery Clyde (Tim Downie) documents his trip to Darkest Peru. He comes across a rather intelligent species of bears. Although he tries to take one in, he decides to bond with them and learns that they can talk and have a great appetite for marmalade. Clyde says he's learned a lot from the bears, and he wonders if the bears have learned anything from him.
Years later, a young bear (voice of Ben Whishaw) awakens to find that the marmalade fruits have been produced. He excitedly runs to his Aunt Lucy (voice of Imelda Staunton) and Uncle Pastuzo (voice of Michael Gambon), the same bears Clyde met. The bears gather the fruits and produce their own supply of marmalade for their sandwiches. That night, an earthquake strikes the forest, wrecking the bears home. Lucy and the little bear hide. When they wake up the next morning, they discover their home is destroyed and Pastuzo is nowhere to be found. All that's left behind is his hat.
Lucy takes the little bear to a ship and places him on a lifeboat with a supply of marmalade. She is going to stay at a home for retired bears while she sends the little one to find a home of his own. The bear eats all the marmalade until he arrives at a train station in London. He tries to find a home from anybody passing by, but they all ignore him. He sits alone with some birds, sharing his marmalade sandwich, when the Brown family walks by. The mother Mary (Sally Hawkins) spots the bear and immediately takes a liking to him, while her husband Henry (Hugh Bonneville) is less than enthused. Their son Jonathan (Samuel Joslin) also likes the bear, while his sister Judy (Madeleine Harris) is not very interested. They treat him to a meal, and Mary decides to name him Paddington.
The Browns take Paddington home where they live with a relative named Mrs. Bird (Julie Walters), only for the night until they turn him in to the authorities. Paddington goes to the bathroom and puts two toothbrushes in his ears, pulling out big chunks of earwax. Curious, he licks one chunk, only to be disgusted. He grabs a bottle of mouthwash and chugs it. The alcohol burns his throat and he dunks his head in the toilet and cools off with the water. Paddington gets his head stuck and overflows the toilet bowl. He pulls himself out and turns on the showerhead. This causes a flood that fills the bathroom with water. Henry opens the door and gets caught in the wave of water. Jonathan thinks its amazing.
At the Natural History Museum, a monkey is delivered to the museum director Millicent (Nicole Kidman). She has sinister plans for the primate, when the man delivering the monkey tells her that he spotted sticky footprints of marmalade around the boat. Millicent's eyes perk up, because she knows what this means and what the man is talking about. She takes a knife and throws it at a picture on the wall of Montgomery Clyde and the bears, along with a collage of other articles and pictures involving this expedition.
During his stay, Paddington learns a thing or two about the Browns - Henry is a real estate agent, Mary is an artist, Judy is seeing a boy named Tony and is learning Chinese to run off there, and Jonathan aspires to be an astronaut. Mary notices Paddington's hat. She says she knows someone who works at an antique shop and might know how to find out who owned that hat.
Mary brings Paddington to the shop owned by Mr. Gruber (Jim Broadbent). As he looks at the hat, a pickpocketing thief (Matt King) comes in and swipes the wallet off another customer. On his way out, he drops it. Thinking it's the man's own wallet, Paddington grabs it and runs after him. The thief runs away, but Paddington continues to give chase. He even gets a police hat and rides with a skateboard and umbrella to catch up with the thief, as townspeople and school children watch. The wind blows the umbrella up high, allowing Paddington to land on the thief and causing him to spill many other wallets he's stolen. The police arrest the thief while Paddington is praised as a hero, even though he still doesn't realize he just caught a thief. When he gets back to the antique shop, the other customers praise him for recovering their stolen wallets. Mr. Gruber then tells Paddington that the hat belonged to a guild of explorers, which is one clue to finding out the identity of the explorer.
Henry begrudgingly accompanies Paddington to the offices of the guild, where the secretary tells them that there are no records on any expeditions to Peru. Paddington then gets Henry to dress up as a maid while they sneak into the computer room to search the archives. They learn that there were a few records on Peru, but they were destroyed. Paddington then accidentally jams the message delivery system with marmalade, forcing him and Henry to run.
Millicent continues her pursuit of Paddington. She even gets help from the Browns' grumpy neighbor Mr. Curry (Peter Capaldi), as he is smitten with Millicent.
At home, the kids start to bond with Paddington. He gets Judy to be more open with him, and he starts teaching her how to speak bear. He helps Jonathan build things with his father's old toys. The kids also give Paddington a bath, after which he shakes off all the water and looks puffy and silly. The parents notice how much the kids enjoy Paddington, to the point where they are considering keeping him around longer.
Paddington is left home alone while the Browns are out. Millicent finds the apartment and attempts to sneak in and grab him. Paddington spots her and, with her gas mask on, he mistakes her for an elephant and runs away. In the struggle, they accidentally cause a fire from the oven. Millicent escapes before anyone notices. When the Browns return, Henry is very upset with Paddington and decides Paddington needs to go.
Paddington leaves a note for the Browns apologizing for the trouble he's caused as he decides to locate Montgomery Clyde on his own. The Browns find the note, and everyone is unhappy with Henry for driving Paddington away. Mary says that he was the best thing that ever happened to the family.
The bear goes all around town looking for people with the name Montgomery Clyde, with no success. At his last stop, he hears a woman's voice saying Clyde was her father. Paddington enters the home, only to discover the voice belongs to Millicent. She kidnaps Paddington and throws him in her taxidermy van. Mr. Curry sees this and discovers her true intentions. She also rejects his romantic advances and leaves. Mr. Curry then calls the Browns and tells them that Paddington is in trouble.
Millicent takes Paddington to the museum and reveals to him that she is indeed Clyde's daughter. Because he failed to bring back the bears from Peru, he was disgraced and kicked out of the guild. He opened a petting zoo, but Millicent now wants to finish what her father failed to do. She prepares to stuff Paddington as the Browns (and Mrs. Bird) make it to the museum. They enter through the sewers to get inside and they kill the power while Mrs. Bird distracts the security guard with a drinking game. Henry heroically climbs out the window and finds the room where Paddington is in and tries to help him get out. However, Millicent turns the power back on and notices the family's wet footprints and realizes she's being sabotaged. Paddington is forced to climb to the roof through the furnace, just as Millicent turns it on. He uses little vacuums to climb up until they start to run out of battery. He nearly falls to his doom until the Browns catch him and pull him up. Millicent makes it to the roof and faces the Browns. She holds up a tranquilizing gun at Paddington, when he spots many birds near him. He takes out a marmalade sandwich and throws it in the air so the birds can fly around Millicent and subdue her. Mrs. Bird then opens a door and pushes Millicent off the roof, although she manages to grab onto a flagpole. The family takes Paddington home.
Paddington writes one more letter to Aunt Lucy telling him about the latest events. Millicent was removed from her position as museum director and was forced to do community service at her father's petting zoo. She is seen getting a pile of poo dumped on her by a cheeky monkey. The Browns are doing better than before now that they've officially adopted Paddington as part of their family. He tells Lucy that he finally has a home. Paddington then joins the Browns outside for a snowball fight.