Popular animated hero Asterix and his faithful sidekick Obelix travel to ancient Egypt to help Cleopatra build a new summer home. Cleopatra and Julius Caesar have made a bet, with Caesar wagering the project cannot be completed in a few weeks time. With the help of a magic potion, Asterix comes to the rescue of the Queen of the Nile as Caesar and an angry architect plot against them.
After a heated argument with Julius Caesar over his lack of faith in the Egyptian people, Queen Cleopatra enters into a bet claiming that she can have a magnificent palace constructed for him in Alexandria within three months. She gives this enormous task to her best architect Edifis (despite his shortcomings), informing him that he will be covered with gold if he succeeds or thrown to the crocodiles if he fails. Daunted and distraught, believing the task to be insurmountable without some sort of magic, Edifis travels to Gaul to seek help from the famous druid Getafix.Getafix agrees to return to Egypt with Edifis, while Asterix and Obelix insist on accompanying them. Obelix further insists that Dogmatix be allowed to join the voyage and smuggles him along despite objections from Asterix. En route to Egypt, Edifis' ship is met by a gang of pirates. Poetic justice rules the day as the pirate ship is boarded by Asterix and Obelix, who scuttle it after a largely one-sided fight. Upon reaching Egypt, it becomes clear that Edifis is not a particularly gifted architect; in Cleopatra's words his buildings are the laughing stock of those who don't live in them. His scheming rival Artifis proposes that they collaborate in order to build Caesar's palace on time and divide the reward between them; the catch being that Edifis alone be thrown to the crocodiles should they fail. Edifis refuses and Artifis swears vengeance, angered further by the injuries he sustains while negotiating Edifis' house (which later collapses altogether).Artifis raises tensions amongst the construction workers by convincing them that they are being exploited by Edifis and encourages them to strike. To win them over and enhance their productivity, Getafix gives the workers his magic potion which enables them to continue effortlessly with the construction of the palace. Getafix refuses to give any to Obelix, much to his disgruntlement. Building progress becomes so rapid that the labourers exhaust their supplies of stone; Artifis has bribed the supplier to dump the subsequent shipment into the Nile and the Gauls are forced to escort a fleet of ships to fetch more. Sightseeing en route, the trio visit the Pyramids at Giza. In his attempt to scale the Sphinx, Obelix provides an outlandish hypothesis as to how the monument came to be without a nose. The Gauls are intercepted by Artifis' sidekick Krukhut, who poses as a guide with the intention of getting the Gauls lost during a tour of the Great Pyramid. Trapped deep within the pyramid, Getafix gives Obelix his first taste of magic potion, presumably to give him the strength to break them out. The Gauls fail to negotiate the maze, but eventually escape after being heroically tracked by Dogmatix. Undeterred, Artifis and Krukhut make a further attempt to prevent the stone reaching its destination by hiring the same gang of pirates seen earlier in the film to attack the fleet on its return to Alexandria. A short second encounter with the pirates alleviates Obelix's boredom, despite their cowardly attempt at retreat. In a final effort to stop the three Gauls, Artifis frames them for an attempt to poison Cleopatra with the gift of a cake made from such ingredients as arsenic, strychnine and vitriol. Asterix, Obelix and Getafix are thrown into the dungeon after the Queen's taster becomes ill from eating the cake. Fortunately, Getafix carries an antidote that enables them to eat the remainder of the cake (giving the impression that it was in fact harmless) as well as curing the taster. The Gauls are pardoned and catch Artifis and Krukhut; their punishment is to work for Edifis as labourers.Cleopatra gloats over the likelihood of winning her bet to Caesar, who fears he will lose face with her should she get the better of him and instructs his spy to infiltrate the building site. Learning that the Gauls and their magic potion are involved, Caesar orders his three mercenaries to kidnap Getafix and imprison him. Two of the mercenaries are caught by Asterix and Obelix, who learn of what has happened to Getafix and promptly free him. In desperation, Caesar holds the construction site under siege and bombards the unfinished palace with boulders. Cleopatra intervenes, forcing Caesar to lift the siege and despite the damage, the palace is completed on schedule. Edifis is honoured and the Gauls are escorted home aboard Cleopatra's luxury ship, much to the displeasure of the sacred crocodiles.