| Subject | English | Russian |
| gen. | let in on a secret | посвятить кого-либо в тайну |
| gen. | let in on a secret | открыть секрет (I'm going to let you in on a little secret. If you tell them that you're a local, they'll give you a nice discount. – открою тебе небольшой секрет ART Vancouver) |
| slang | let in on a secret | сказать по секрету (how did you do it, let me in on a secret Damirules) |
| idiom. | let in on a secret | поведать секрет (If you let someone in on something that is a secret from most people, you allow them to know about it. george serebryakov) |
| gen. | let smb. in on a secret | посвятить кого-л. в тайну |
| gen. | let in on secrets | посвящать в секреты (VLZ_58) |