Não acredito!

Drop this phrase whenever reality catches you off guard. You can say it flatly if you are annoyed. You can scream it if you are excited. Often, people stretch the vowels for emphasis: Nãaaaao acredito!. In text messages, you might see it as ñ acredito or followed by many exclamation points. It is a complete sentence on its own. You do not need to add anything else to make your point.

Use it when a friend tells you they won the lottery. Use it at a restaurant if they just ran out of your favorite dessert. It is perfect for reacting to news, both good and bad. If you are watching a movie and there is a massive plot twist, this is the phrase to mutter. It makes you sound like a natural part of the conversation.

Avoid using this in very serious or tragic situations where 'disbelief' might seem dismissive. If someone shares a deep personal tragedy, a simple Sinto muito (I'm sorry) is better. Do not use it in a formal legal or scientific context where you are literally stating a lack of evidence. In those cases, use Não creio or a more formal structure. Also, try not to use it if someone is explaining a simple fact you just didn't know; it might make you look a bit dramatic.

Portuguese speakers are generally expressive and emotive. Não acredito reflects this cultural trait perfectly. It is not just about the words; it is about the shared energy of the moment. In Brazil, you might hear Mentira! (Lie!) used in the exact same way. In Portugal, the tone might be slightly more reserved but the sentiment remains. It bridges the gap between simple observation and emotional reaction.

If you want to sound more informal, try Sério? (Seriously?). For a more 'street' vibe in Brazil, you can use Tá brincando! (You're joking!). If you are truly shocked, you can add Eu at the start: Eu não acredito nisso!. Another common one is Não pode ser! (It can't be!). Each adds a slightly different flavor to your disbelief, but Não acredito remains the classic choice.