Twelve-year-old Emil, son of a poor single mother, is sent to Berlin for the first time in his life, to bring 140 marks (about a month's income of his mother; it's seven pounds in some versions) to his grandma, for financial support. But when he falls asleep on the train, a man who calls himself Grundeis steals the money from him. Fortunately he meets Gustav with the signal horn, who's the leader of a children's gang and willing to help him catch the guy.
The novel received a sequel, Emil and the Three Twins. It's been adapted for film, television and the stage, and some well-known creators have worked on the various movie versions; Billy Wilder wrote the screenplay for the 1931 film, while Disney produced an adaptation in 1964.
- An Aesop: Parodied by the grandma: "Never send cash always use postal service."
- Before that, Emil and his mother propose two rather reasonable aesops—Emil says he'll not be likely to trust a stranger again, and his mother says she's learned that children should not travel alone.
- Author Tract: There are many poor people in the world suffering. The world is unfair, And That's Terrible.
- Chekhov's Gun: Emil used a pin to make the bank notes stick in his pocket. When "Grundeis" wants to exchange the three notes in a bank, Emil remembers Just in Time that the notes have pinholes.
- "Could Have Avoided This!" Plot: Near the end of the book, when Emil is being interviewed by reporters, one of them wonders aloud why Emil didn't just go to the police to report the theft of his money. Much earlier prior to this, too, when Emil first meets Gustav, the latter points out a policeman that Emil could make a report to right then and there. However, the reason Emil never goes that route is because of the Felony Misdemeanor he'd committed earlier.
- Creator Cameo: Kästner later appears in the story to write an article about the boys. And also had a minor role in one movie.
- Disappeared Dad: Emil only lives with his mother. Emil is twelve years old in the story, the book was published in 1929, so it is quite likely that his father died in World War I.
- Does Not Like Spam: Emil can't bear fish. When one of the boys asks why, Pony explains that fish makes Emil sick.
- Evil Is Petty: Grundeis. He's a successful bank robber who has stolen over ten thousand marks (a six digit sum in today's money), but he still drugs a boy, fleeces his unconscious body and takes the comparably measly 140 marks from him just for kicks.
- Felony Misdemeanor: Emil participated in a prank in his hometown. For the record: They put an old hat on a monument of some famous guy, and Emil had to paint the monument's nose red, and add a moustache. After this, he has a bad conscience and becomes afraid of policemen. That's why he doesn't dare to tell the police.
- Film of the Book: Several. The script of the 1931 film was written by a then-unknown Billy Wilder.
- The Flapper: Pony Hütchen, though she is a little girl. She wears a fringe haircut (="Pony" in German) which was the fashion at this time, and a little hat (=Hütchen). And she is quite outspoken (not to say: bratty), especially for her time, and challenges Emil to a fight. (Being a Nice Guy who Wouldn't Hit a Girl, and several pounds heavier than her, he declines of course.)
- Free-Range Children: Probably nowadays not many people would send a 12-year-old boy to a metropolis to deliver a month's wage of money.
- Minor Crime Reveals Major Plot: After Grundeis is arrested for the theft, further investigation reveals him to be a bank robber.
- Mustache Vandalism: Emil is reluctant to approach the police and instead uses the help of other children. The reason is that a few weeks earlier he painted a beard and mustache on a statue, so he's afraid the police won't believe him.
- Narrative Profanity Filter: "And then, Petzold said a very bad word and left." It fits in with the moralistic tone of the book.
- Nice Hat: "Grundeis" wears a bowler hat.
- Only Known by Their Nickname: Pony Hütchen. We never find her true name.
- Person with the Clothing: The narration tends to refer to "Grundeis" as "der Mann im steifen Hut" ("the man in the stiff hat") since he's noticeably inconsistent about what his name is in an "I Have Many Names" way.
- Screw the Money, I Have Rules!: The boys get an offer to make advertising for several firms, after becoming famous, but decide against it.
- The Smart Guy: The Professor, one of the boys helping Emil in his chase. He actually takes something of a leadership role among the group and shares The Lancer status with Gustav.
- The Sociopath: "Grundeis". While him making up tall tales in order to make fun of Emil may be glossed over; his other actions certainly fit the bill - like drugging a boy and robbing him blind (even though he himself has thousands of marks sewn into his jacket; and the kid is from an impoverished background who sorely needs the money), or being a pathological liar (he constantly makes up new names even after a point where doing so has stopped being useful).
- Tall Tale: "Grundeis" makes fun of Emil, telling the inexperienced small-city-boy that people in Berlin sometimes leave their brain at the bank to get a loan (among other ridiculous things), and is immediately called out by another passenger.Grundeis: Ever seen builings a hundred stories high? No, I thought as much. But you will in Berlin. They've had to fasten the roofs to the sky so they don't blow away...then, if you're in a terrible hurry to get anywhere, you just go to the nearest post office and they'll pack into a box and shoot you through a tube to the post office in the district you want to go to...yes, and if you haven't any money, you can just go to the bank and they'll give you fifty pounds in exchange for your brains. Of course, you can't live without your brain—only a day or two—and to get it back you'll find you have to pay the bank sixty pounds. The doctors, too, they've got some marvelous cures...Passenger: It sounds to me as if you must have left your own brain at the bank the last time you were there. Stuffing the boy with such nonsense!
- Trademark Favorite Food: For Emil, it's macaroni-cheesenote with ham in it. His mother makes a special point of preparing it for him before he sets out for Berlin.
- Would Hurt a Child: At one point "Grundeis" slaps the Professor in the face. Unfortunately for him, the Professor is more than willing to punch him back.