Maurice Denham provided the voice for all the animals in the film.
Manor Farm is a formerly prosperous farm that has fallen on hard times, and suffers under the now-ineffective leadership of its aggressive and drunken owner, Mr. Jones. One night, Old Major, the prize boar, and the second-oldest animal on the farm, calls all of the animals on the farm together for a meeting, where he compares the humans to parasites and encourages the animals to break free from their tyrant's influence, while reminding them that they must hold true to their convictions after they have gained freedom. With that, he teaches the animals a revolutionary song before collapsing dead mid-song to the animals' horror.
The next morning, Mr. Jones neglects to feed the animals for breakfast, and they decide to break into the storehouse to help themselves. When Mr. Jones wakes up and threatens them with his whip, the animals revolt and drive the drunken and irresponsible farmer away from the farm, and renaming it "Animal Farm". They begin destroying every trace of the farmer's influence, starting with the weapons used against them. The people of the surrounding area rally against them, but are beaten back after a fierce fight. A subsequent investigation of the farmhouse leads them to concede against living there, though one of the head pigs, an antagonistic boar named Napoleon, takes interest in the abandoned house, and even more so in a litter of puppies left motherless.
The Seven Commandments of Animalism are written on a wall of the barn to illustrate their community's laws. The most important is the seventh, which says that "All animals are equal." All the animals work, but the workhorse, Boxer, and his friend Benjamin the donkey, who is also the film's protagonist, put in extra work. Snowball attempts to teach the animals reading and writing; food is plentiful, and the farm runs smoothly. The pigs elevate themselves to positions of leadership, and set aside special food items ostensibly for their personal health. Napoleon takes the pups and trains them privately.
When Snowball announces his idea for a windmill, Napoleon opposes it. Snowball makes a speech in favor of the windmill, whereupon Napoleon has his dogs chase Snowball and kill him. Afterwards, Napoleon declares himself leader, along with Squealer as his propagandist, and makes changes. Meetings will no longer be held, but instead a committee of pigs will run the farm. The animals eventually work harder because of the promise of easier life once the windmill is completed.
During this time, the pigs also decide to alter their own laws. "No animal shall sleep in beds," is changed to "No animal shall sleep in beds with sheets," when the pigs are discovered to have been sleeping in the old farmhouse. Before long, Napoleon's greed drives him to negotiate with a local trader named Mr. Whymper for a supply of both jellies and jams. The price is all of the hens' eggs. When the hens discover this, they attempt to revolt by throwing their eggs at the pigs during an attempted seizure by force. To instill fear, Napoleon holds a "trial," and a sheep and duck join the hens accused as traitors. They are taken outside and murdered by the dogs, with their blood used to edit a commandment; "No animal shall kill another animal" becomes, "No animal shall kill another animal without cause". After their deaths, the revolutionary song is banned by Napoleon because he claims the dream of Animal Farm has been realized, and the revolution is over. He also threatens that the penalty for animals caught singing the song is death.
Growing jealous of Whymper's financial success due to his trading with Animal Farm, a hostile group of farmers attack the farm. Mr. Jones, shunned for his failure and drunkenness, uses blasting powder to blow up the windmill. Though the animals win the battle, they do so at a great cost of lives, and Boxer is wounded. Boxer continues working until he collapses one night, while working on rebuilding the windmill. Napoleon sends for a van to take Boxer away, which Benjamin recognizes as the "death wagon" from Whymper's glue factory. That night, a supply of alcohol is delivered. The next day, Squealer delivers a phony speech, claiming to have been at Boxer's side at his deathbed, and states that his last words were to glorify Napoleon. The upset animals see through the propaganda, and recognize how dictatorial Napoleon has become, but are driven away by the snarling dogs before anything can be done.
Years pass, and the pigs have now learned to both walk upright and wear clothes. The Seven Commandments are reduced to a single phrase: "All animals are equal, but some animals are more equal than others". Napoleon holds a dinner party for a delegation of outside pigs, who congratulate him on having the hardest-working and lowest-consuming animals in the country. Napoleon gives a toast to a future where pigs own and operate farms everywhere.
Benjamin, overhearing the conversation, imagines the faces of all the pigs assuming the likeness of Mr. Jones, as he realizes the similarity between the two. Realizing that things have become "worse than ever for ordinary creatures," all of the animals unite to overthrow Napoleon. The animals march upon the farmhouse, forcing Napoleon to call his guard dogs for help, only to see the dogs are now drunk. The pigs are unable to overpower their infuriated attackers. Napoleon, now helpless, is unable to defend himself as his fellow pigs are trampled to death (Off-screen). Benjamin stands in grim triumph as he and his fellow animals retake the farm.
The animation historian Brian Sibley doubts that the team responsible was aware of the source of the funding initiating the project, which came from the Central Intelligence Agency to further the creation of anti-communist art.
The "financial backers" influenced the development of the film - the altered ending, and that the message should be that, "Stalin's regime is not only as bad as Jones's, but worse and more cynical," and Napoleon, "not only as bad as JONES but vastly worse". And the "investors" were greatly concerned that Snowball (the Trotsky figure) was presented too sympathetically in early script treatments, and that Batchelor's script implied Snowball was "intelligent, dynamic, courageous". This implication could not be permitted. A memo declared that Snowball must be presented as a, "fanatic intellectual whose plans if carried through would have led to disaster no less complete than under Napoleon". De Rochemont accepted this suggestion.
Halas and Batchelor were awarded the contract to make the feature in November 1951 and it was completed in April 1954. The production employed about 80 animators.
Much of the pre-release promotion for the film in the UK focused on it being a British film instead of a product of the Hollywood studios.
To coincide with the film's release, a comic strip version was serialised in newspapers, drawn by Harold Whitaker, one of the animators.
Scenes from Animal Farm, along with the 1954 TV program Nineteen Eighty-Four, were featured in "The Two Winstons," the final episode of Simon Schama's program A History of Britain.
Film critic C. A. Lejeune wrote at the time: "I salute Animal Farm as a fine piece of work… [the production team] have made a film for the eye, ear, heart and mind". Matyas Seiber's score and Maurice Denham's vocal talent have been praised specifically (Denham provided every voice and animal noise in the film). The animation style has been described as "Disney-turned-serious". The movie holds a 63% score at Rotten Tomatoes based on 8 reviews,
Some criticism was levelled at the altered ending, with one paper reporting, "Orwell would not have liked this one change, with its substitution of commonplace propaganda for his own reticent, melancholy satire".
In 1954 Harold Whitaker, one of the film's animators, adapted the film into a comic strip published in various British regional newspapers.
The Clash used an image from the film on their 45-RPM single "English Civil War". Gorillaz used footage from the film behind Benjamin Clementine in an animated elevator in the recent 2017 music video single Hallelujah Money.
The 'Special Edition' DVD includes a documentary hosted by Tony Robinson. A 2004 DVD release of the film from Digiview Productions also exists.