To say “don’t lie” in Spanish, use “no mientas” (informal, singular) or “no mienta” (formal, singular), with the form depending on who you’re addressing.
You’re in a conversation with a close friend who just stretched the truth about their weekend. You want to say “don’t lie” in Spanish, but a split-second hesitation hits—should it be something with “mientes” or “mientes”? And what if you’re talking to your boss? The answer isn’t as simple as one phrase fits all.
Spanish makes a clear distinction between informal and formal commands, and the verb “mentir” (to lie) throws a stem change into the mix. This article breaks down the exact phrases you need, explains the grammar behind them, and shows you when to use each form so you never second-guess yourself.
The Three Forms Of “Don’t Lie”
The most direct translation of “don’t lie” depends entirely on who you’re talking to. For a friend, sibling, or someone your age, use “no mientas” (informal tú). This is the form you’ll hear in everyday conversations and on TV shows between peers.
For a stranger, an elder, or anyone in a position of authority, switch to “no mienta” (formal usted). It adds the same distance and respect that English conveys through tone. If you’re addressing a group—say, a classroom or a team—use “no mientan” (ustedes) throughout Latin America.
In Spain, there’s also the plural informal form “no mintáis” (vosotros), but you’ll rarely need it outside of the Iberian Peninsula. Stick with “no mientan” for groups in most contexts and you’ll be understood everywhere.
Why Getting The Form Right Matters
Spanish speakers pay close attention to formality in commands. Using “no mientas” with a professor can come across as disrespectful, while using “no mienta” with a close friend might feel stiff or distant. Mastering these distinctions avoids awkward moments and shows cultural awareness.
- Friends and family (tú): “No mientas” is your default. It signals closeness and trust. Example: “No mientas, sé que fuiste al parque” (Don’t lie, I know you went to the park).
- Respect and authority (usted): “No mienta” is for people you don’t know well or who hold a higher status. Example: “Por favor, no mienta en su declaración” (Please don’t lie in your statement).
- Groups (ustedes): “No mientan” works for any group—formal or informal—across Latin America. Example: “No mientan, ya sabemos la verdad” (Don’t lie, we already know the truth).
- Regional variation (vosotros): In Spain, “no mintáis” is the informal plural, but it’s rarely heard elsewhere. If you’re learning European Spanish, practice it; otherwise, skip it.
- Common mistake to avoid: Don’t use the affirmative imperative (“miente” or “mentid”) for negative commands. Spanish always requires the subjunctive after “no.”
The payoff for getting this right is huge—you’ll sound natural and respectful, and native speakers will notice you’ve taken the time to learn the nuances.
How Negative Commands Actually Work In Spanish
English simply adds “don’t” before the verb: “don’t lie.” Spanish uses a different structure entirely—the present subjunctive mood. Per the Negative Commands Subjunctive guide from the University of Kansas, negative tú commands are formed by taking the “yo” form of the present tense, dropping the “-o,” and adding the opposite vowel endings. For -er and -ir verbs like “mentir,” that means adding “-as” for tú and “-a” for usted.
“Mentir” is an e>ie stem-changing verb, so the stem shifts from “ment-” to “mient-” before adding those endings. That’s why you get “no mientas” instead of “no mentas.” The same rule applies to similar verbs like “sentir” (to feel) → “no sientas” and “preferir” (to prefer) → “no prefieras.”
Once you understand this pattern, you can form negative commands for almost any verb. The subjunctive might seem intimidating at first, but for negative commands it follows a consistent, predictable template.
| Verb | Negative Tú Command | Stem Change |
|---|---|---|
| Mentir (to lie) | No mientas | e → ié |
| Decir (to say/tell) | No digas | e → i |
| Comer (to eat) | No comas | None |
| Vivir (to live) | No vivas | None |
| Dormir (to sleep) | No duermas | o → ué |
| Repetir (to repeat) | No repitas | e → i |
Notice how regular -er and -ir verbs simply change the vowel ending, while stem-changing verbs like “dormir” and “repetir” also alter the root. This is why memorizing the pattern pays off across dozens of verbs.
Common Phrases With “Don’t Lie”
Once you know the basic command, you can expand it with pronouns to create more specific expressions. These phrases are useful in real conversations—from friendly teasing to serious requests.
- “Don’t lie to me”: “No me mientas” (informal) or “no me mienta” (formal). The object pronoun “me” (me) goes between “no” and the verb. For example: “No me mientas, solo quiero saber la verdad” (Don’t lie to me, I just want to know the truth).
- “Don’t lie to yourself”: “No te mientas” (informal) or “no se mienta” (formal) uses the reflexive pronoun “te” or “se.” Example: “No te mientas, sabes que no es cierto” (Don’t lie to yourself, you know it’s not true).
- “Don’t be a liar”: “No seas mentiroso/a” uses the verb “ser” (to be) rather than “mentir.” This phrase works when you’re accusing someone of being dishonest as a character trait. Example: “No seas mentiroso, todos vimos lo que pasó” (Don’t be a liar, we all saw what happened).
- “Don’t lie to us”: “No nos mientas” (informal) or “no nos mienta” (formal) includes the plural object pronoun “nos” (us). Example: “No nos mientas, estamos de tu lado” (Don’t lie to us, we’re on your side).
Remember that pronoun placement is strict in negative commands: pronouns always attach to the end in affirmative commands (e.g., “dímelo” – tell it to me), but in negative commands they sit between “no” and the verb (e.g., “no me lo digas” – don’t tell it to me). This is a common area of confusion, so practice with a few examples until it feels natural.
Mastering The Verb Mentir
To use “mentir” confidently in any situation, you need to understand its full conjugation—especially the present subjunctive, which powers all negative commands. The full conjugation chart found on Ellaverbs’ Mentir Conjugation page shows how the e>ie stem change applies across most tenses.
In the present subjunctive, the stem “mient-” appears in all forms except nosotros and vosotros, where it reverts to “mint-” (note the i instead of ie). This pattern is the same for all e>ie stem-changing -ir verbs. For example, “sentir” becomes “sienta, sientas, sienta, sintamos, sintáis, sientan.”
Practicing the subjunctive aloud helps internalize the rhythm. Try saying “no mientas, no mienta, no mientan” a few times. Once the pattern clicks, you’ll be able to form negative commands for stem-changing verbs without thinking.
| Person | Present Subjunctive of Mentir |
|---|---|
| Yo | Mienta |
| Tú | Mientas |
| Él/Ella/Usted | Mienta |
| Nosotros | Mintamos |
| Vosotros (Spain) | Mintáis |
| Ellos/Ellas/Ustedes | Mientan |
Notice the stem change disappears in the nosotros and vosotros forms. This is a quirk of e>ie stem-changing verbs—the stress shifts away from the stem, so the change is not triggered. Keep this in mind when using “no mintamos” (let’s not lie) or “no mintáis” (don’t lie, plural informal Spain).
The Bottom Line
Saying “don’t lie” in Spanish comes down to two key points: choose the right formality (tú, usted, or ustedes) and use the present subjunctive with a stem change. For daily use, “no mientas” will cover most of your informal conversations, while “no mienta” keeps things respectful in formal settings. Add object pronouns like “me” or “te” to create phrases like “no me mientas” (don’t lie to me).
If you’re preparing for a conversation with native speakers or working toward an official language proficiency exam like the DELE, practicing these commands aloud with a native-speaking tutor can iron out the pronoun placement and stem change before you use them in real life.