Minions are small, yellow creatures who have existed since the beginning of time, evolving from single-celled organisms into beings who exist only to serve history's most villainous masters. They speak their own language, Minionese, a conlang consisting of funny sounding words from Italian, Korean, and other languages. They find great masters—including a T-Rex, a caveman, an Egyptian pharaoh, Dracula, and Napoleon,—but after accidentally killing nearly all of them with their incompetence, they decide to isolate themselves from the world and start a new life in Antarctica. By 1968, the lack of a master to serve drives them into depression, so Kevin, one fearless Minion, plans to find a new one for them by going back out into the world.
Stuart—a bored, teenaged minion who is obsessed with guitars—joins him reluctantly, as does an over-enthusiastic Bob, whom Kevin only chooses because of no one else willing to volunteer. After a long journey, the Minions arrive in New York, where they soon learn about Villain-Con, a convention to be held in Orlando where supervillains gather from around the world. They hitchhike to Orlando, where they successfully become the henchmen for Scarlet Overkill, the world's first female supervillain. As Scarlet takes the Minions to her home to London, Kevin immediately notifies the other Minions back home. In Antarctica, the other Minions begin working for a Yeti, but once again accidentally kill their leader. Fleeing from the Yeti's angry friends, they travel around the world to find Kevin, who had already told them to meet the trio in England. Scarlet and the Minions arrive at her home, where she orders them to steal St. Edward's Crown from Queen Elizabeth II of England and later shows through a bedtime story that she'll kill them if they fail. With gadgets from Herb, Scarlet's husband, the Minions successfully break into the Tower of London. However, the crown is being delivered to the Queen, so they steal it from her while she's in her carriage, with the police in pursuit. Bob crashes onto the mythical Sword in the Stone and pulls the sword, Excalibur, out to defend himself. After he has pulled out the legendary sword, Elizabeth II is immediately removed from the throne and Bob is crowned as the new King of England. Convinced they are traitors for stealing her dream, Scarlet confronts the Minions and threatens to execute them for good. King Bob abdicates in Scarlet's favor, but she still doesn't forgive the Minions, locking them in the palace dungeon to be tortured by Herb. The Minions' unusual physiology prevent them from being affected by the torture and Herb eventually leaves to attend his wife's coronation. The Minions then escape the dungeon through a sewer, intending to apologize to Scarlet. At Westminster Abbey, the Minions accidentally interrupt Scarlet's coronation by unscrewing a chandelier, which falls and crushes Scarlet before she can be crowned. Scarlet survives and orders those attending the coronation—including some super-villains—to get the Minions. Stuart and Bob are captured while Kevin hides in a bar where he finds Elizabeth. Kevin learns that Stuart and Bob are to be executed and breaks into Herb's laboratory, with villains chasing him. He accidentally triggers an experimental machine that enlarges him, destroying the Overkill residence in the process, which scares the villains away. Kevin rescues his companions just as the other Minions arrive in London. Scarlet is distracted by the army of Minions and Kevin knocks her through numerous buildings. She sends a missile towards Kevin, which he swallows, sacrificing himself to save Stuart, Bob and the other Minions. Scarlet and Herb attempt to escape using her dress rocket but Kevin holds onto it as the missile inside him explodes, apparently killing Scarlet and Herb and shrinking Kevin back to his original size. Elizabeth is once again crowned Queen of England, and she publicly thanks the Minions by presenting Bob with a tiny crown, Stuart with an electric guitar and Kevin with a knighthood. Scarlet and Herb, who are suddenly revealed to be alive, then steal the Queen's crown, but they got frozen by young Gru, who takes the crown from them. As the Minions then see that Gru is the perfect new potential boss, they start to go after him, as Bob gives his crown to Scarlet, who is upset over her dream not coming true. The film ends with the Minions chasing Gru to his home.