Let the cat out of the bag: meaning, examples and when to use it
Short answer: “Let the cat out of the bag” means to tell a secret by mistake. You say it when someone reveals something that was meant to stay hidden: “I let the cat out of the bag.”
What does “Let the cat out of the bag” mean in English?
A secret is like a cat in a closed bag. If the bag opens, the cat runs away and you cannot get it back. In the same way, a secret cannot be taken back after you tell it. The idiom is usually about a mistake, not an on-purpose act.
Examples of “Let the cat out of the bag”
- I let the cat out of the bag when I said the new date.
A mistake in a normal sentence. - Don't let the cat out of the bag before the party.
A warning to keep a secret. - She let the cat out of the bag about the surprise gift.
She told the secret without meaning to.
When do you use “Let the cat out of the bag”?
- When someone tells a secret without meaning to.
- To warn a friend to keep a surprise.
- In speech and in stories.
Is “Let the cat out of the bag” formal?
“Let the cat out of the bag” is informal. It is fine with friends and in stories. In a formal text, write “reveal by mistake”.
Common mistakes with “Let the cat out of the bag”
- It is about secrets, not animals.
- It is usually by mistake. If someone tells a secret on purpose, use “spill the beans”.
- Say “let the cat out of the bag”, not “let the cat out of the box”.
Similar expressions
- Same idea: “spill the beans”, which is not always by mistake. See idioms for talking with people. The origin of this idiom is often told in different ways, so this page does not give one.
Questions
What does “Let the cat out of the bag” mean in English?
“Let the cat out of the bag” means to tell a secret by mistake. You say it when someone reveals something that was meant to stay hidden: “I let the cat out of the bag.”
Is “Let the cat out of the bag” formal?
“Let the cat out of the bag” is informal. It is fine with friends and in stories. In a formal text, write “reveal by mistake”.
What is the difference between “let the cat out of the bag” and “spill the beans”?
Both mean to tell a secret. “Let the cat out of the bag” usually means that you told it by mistake.
Is there a real cat?
No. The cat is only part of the picture. The idiom is about secrets.
Part of the English idioms guide and of idioms for talking with people, in the 💬 Idioms tool.
Written for English learners by the English for Fun team. How we write our lessons · Last updated 2026-11-05.