French grammar · Intermediate
Au Cas Où in French: Saying In Case with the Conditional
French says in case with au cas où, and unlike almost every other conjunction it is followed by the conditional, not the present or the subjunctive. Au cas où tu aurais faim, il y a du pain. On its own at the end of a sentence, au cas où means just in case.
Prends un parapluie, au cas où il pleuvrait.
Take an umbrella, in case it rains.
What it is
Au cas où introduces a possibility you are preparing for rather than expecting. Because the event is hypothetical, French puts the verb in the conditional, which is the mood reserved for things that depend on something else. That makes au cas où one of the very few conjunctions in the language that governs the conditional, and the only one you are likely to need every week.
Je te laisse mon numéro, au cas où tu aurais besoin de moi. — I'll leave you my number, in case you need me.
How to spot it
If the clause describes a precaution against something that may or may not happen, you want au cas où plus a conditional. If it describes a genuine condition the outcome depends on, you want si plus the present.
- Au cas où il serait absent, appelle-moi. — In case he's away, call me.
- Prends de l'argent liquide, au cas où. — Take some cash, just in case.
- Au cas où tu ne l'aurais pas remarqué… — In case you hadn't noticed…
- Emporte une veste au cas où il ferait froid. — Take a jacket in case it gets cold.
The où carries a grave accent and never changes. Writing au cas ou without it turns the phrase into in the case or, which means nothing.
Au Cas Où Quick Reference
Au cas où and its relatives
| Phrase | Followed by | Example |
|---|---|---|
| au cas où | conditionnel | au cas où il viendrait — in case he comes |
| au cas où (alone) | nothing | prends-en, au cas où — take some, just in case |
| dans le cas où | conditionnel | dans le cas où vous accepteriez — should you accept |
| pour le cas où | conditionnel | pour le cas où ça tournerait mal — in case it goes wrong |
| si jamais | présent or imparfait | si jamais tu le vois — if you ever see him |
| des fois que | conditionnel, very informal | des fois qu'il serait là — in case he's around |
| si | présent | si tu viens — if you come |
Common Au Cas Où Examples in French
Au cas où in the sentences where it actually appears:
Taking Precautions
- Je prends mon chargeur au cas où la batterie tomberait à plat.
- I'm taking my charger in case the battery dies.
- Note l'adresse, au cas où tu te perdrais.
- Write down the address in case you get lost.
- On a réservé une table au cas où il y aurait du monde.
- We booked a table in case it's busy.
- Garde une copie au cas où le fichier disparaîtrait.
- Keep a copy in case the file disappears.
The main clause is nearly always an instruction or a precaution already taken.
Polite Offers and Hedges
- Au cas où cela vous intéresserait, la conférence est gratuite.
- In case you're interested, the talk is free.
- Au cas où vous auriez des questions, écrivez-moi.
- Should you have any questions, write to me.
- Je vous joins le document au cas où il vous serait utile.
- I'm attaching the document in case it's useful to you.
- Au cas où vous ne pourriez pas venir, prévenez-nous.
- In case you can't come, let us know.
In formal writing and email, au cas où is a standard politeness device, close to English should you.
Au Cas Où on Its Own
- Prends une deuxième clé, au cas où.
- Take a second key, just in case.
- J'ai apporté du dessert, au cas où.
- I brought dessert, just in case.
- Mets ton maillot, au cas où.
- Bring your swimsuit, just in case.
- On sait jamais, au cas où.
- You never know, just in case.
Used alone it comes at the very end, after a comma, and needs no verb at all.
Looking Back at a Possibility
- Au cas où tu aurais oublié, la réunion est à neuf heures.
- In case you've forgotten, the meeting is at nine.
- Au cas où elle serait déjà partie, laisse un mot.
- In case she's already left, leave a note.
- Au cas où vous n'auriez pas reçu mon message, le voici.
- In case you didn't get my message, here it is.
- Au cas où ils se seraient trompés, vérifie les chiffres.
- In case they got it wrong, check the figures.
For something that may already have happened, use the conditionnel passé: aurais oublié, serait partie.
How Au Cas Où Works
One conjunction, one mood, and a few habits about where it sits in the sentence.
The Conditional Is Compulsory
Au cas où presents an event as merely possible, and the conditional is the mood French uses for events that hang on something else. The present indicative is simply not available after it.
Au cas où il arriverait en avance, laisse-lui la clé.
In case he arrives early, leave him the key.
au cas où + conditionnel.
The Clause Can Go First or Last
Putting au cas où first foregrounds the risk; putting it last treats the precaution as an afterthought. Both are correct, and the comma is required only when the clause comes first.
Emporte des piles, au cas où la lampe s'éteindrait.
Take some batteries, in case the lamp goes out.
Either end of the sentence works.
Use the Conditionnel Passé for Something Already Possible
When the hypothetical event may have happened before you spoke, switch to the past conditional. This is the form behind the very common au cas où tu aurais oublié.
Au cas où vous auriez déjà payé, ignorez ce message.
In case you've already paid, ignore this message.
Past possibility → aurais / serais + participle.
Negation Sits Inside the Clause
Ne and pas surround the conditional form of the auxiliary or the verb, exactly as they would in any other clause. Nothing special happens because of au cas où.
Au cas où tu ne pourrais pas venir, préviens-moi.
In case you can't come, let me know.
Normal negation rules apply.
Au Cas Où Is Not Si
Si sets up a condition that decides the outcome; au cas où sets up a contingency you are insuring against. Si tu viens, on mangera assumes coming is on the table, while au cas où tu viendrais treats it as unlikely but possible.
Si tu viens, préviens-moi ; au cas où tu viendrais, la clé est sous le pot.
If you come, let me know; in case you come, the key is under the pot.
si = condition, au cas où = precaution.
Common Mistakes with Au Cas Où
Incorrect: Au cas où il vient, préviens-moi. — In case he comes, let me know.
Correct: Au cas où il viendrait, préviens-moi. — In case he comes, let me know.
Au cas où always takes the conditional. English uses a present after in case, so the present indicative gets carried over, but French treats the event as hypothetical and marks it in the verb.
Incorrect: Au cas où il vienne, préviens-moi. — In case he comes, let me know.
Correct: Au cas où il viendrait, préviens-moi. — In case he comes, let me know.
The subjunctive is the natural guess, since most French conjunctions that express uncertainty take it. Au cas où is the exception, and it is the conditional that follows.
Incorrect: Prends une carte, en cas. — Take a map, just in case.
Correct: Prends une carte, au cas où. — Take a map, just in case.
En cas exists only inside longer phrases such as en cas de pluie or en cas d'urgence, always followed by de and a noun. Standing alone, the phrase is au cas où.
Incorrect: Au cas où tu as oublié, la réunion est à neuf heures. — In case you've forgotten, the meeting is at nine.
Correct: Au cas où tu aurais oublié, la réunion est à neuf heures. — In case you've forgotten, the meeting is at nine.
A possibility that may already be true still needs the conditional, just in its past form. The passé composé would assert that the forgetting really happened.
The Conditional You Need After Au Cas Où
The conditional is built from the future stem plus the imparfait endings, so if you can form the future you already know most of it. These tables cover the regular pattern, the irregular stems that come up in precautions, and the past conditional.
Regular Conditional Endings
Take the infinitive, drop the final e of an -re verb, and add -ais, -ais, -ait, -ions, -iez, -aient.
| Pronoun | parler | finir | vendre |
|---|---|---|---|
| je / j' | parlerais | finirais | vendrais |
| tu | parlerais | finirais | vendrais |
| il / elle / on | parlerait | finirait | vendrait |
| nous | parlerions | finirions | vendrions |
| vous | parleriez | finiriez | vendriez |
| ils / elles | parleraient | finiraient | vendraient |
Every conditional form has an r before the ending, inherited from the infinitive.
Irregular Stems That Turn Up in Precautions
Être, avoir, venir and the impersonal pleuvoir account for a large share of real au cas où sentences.
| Pronoun | être (ser-) | avoir (aur-) | venir (viendr-) | pleuvoir (pleuvr-) |
|---|---|---|---|---|
| je / j' | serais | aurais | viendrais | — |
| tu | serais | aurais | viendrais | — |
| il / elle / on | serait | aurait | viendrait | pleuvrait |
| nous | serions | aurions | viendrions | — |
| vous | seriez | auriez | viendriez | — |
| ils / elles | seraient | auraient | viendraient | — |
Pleuvoir exists only in the third person singular, so il pleuvrait is the whole conjugation.
The Past Conditional
Avoir or être in the conditional, plus the past participle. Use it when the possibility may already be a fact.
| Pronoun | avoir + oublié | être + parti |
|---|---|---|
| je / j' | aurais oublié | serais parti(e) |
| tu | aurais oublié | serais parti(e) |
| il / elle / on | aurait oublié | serait parti(e) |
| nous | aurions oublié | serions parti(e)s |
| vous | auriez oublié | seriez parti(e)(s) |
| ils / elles | auraient oublié | seraient parti(e)s |
Au cas où tu aurais oublié is so frequent that it is worth learning as a fixed opening.
Other Ways to Say Just in Case
Au cas où is the neutral choice, but French has a register spread from very formal to very casual, and the mood changes with it.
Si jamais
Common in speech and followed by the indicative, not the conditional. It leans slightly more towards if it ever happens than towards a planned precaution.
- Si jamais tu le croises, dis-lui bonjour.
- If you ever run into him, say hello.
- Si jamais ça ne marche pas, rappelle-moi.
- If it doesn't work, call me back.
- Si jamais j'avais su, je serais venu.
- Had I known, I would have come.
Si jamais takes si rules: present for a real possibility, imparfait for a remote one, never the conditional.
Dans le cas où and pour le cas où
Both are more formal versions of au cas où and both keep the conditional. They belong in contracts, official letters, and careful writing.
- Dans le cas où vous refuseriez, le contrat serait annulé.
- Should you refuse, the contract would be cancelled.
- Pour le cas où un retard surviendrait, prévenez le service.
- In case a delay occurs, notify the department.
- Dans le cas où les deux parties seraient d'accord, la vente est conclue.
- In the event that both parties agree, the sale goes through.
Dans le cas où is the phrase you will meet in administrative French; au cas où is the one you will say out loud.
Casual alternatives
Spoken French has a handful of short precautionary phrases that need no clause at all, or take one very loosely.
- On ne sait jamais.
- You never know.
- Par précaution, j'ai pris deux billets.
- As a precaution, I took two tickets.
- Des fois qu'il y aurait du monde.
- In case it's crowded.
- À tout hasard, tu as son numéro ?
- On the off chance, do you have his number ?
Des fois que is regional and very informal, but it does take the conditional like au cas où.
Au Cas Où FAQs
- How do you say just in case in French?
- Au cas où, placed at the end of the sentence after a comma and with no verb after it: prends ton parapluie, au cas où. If you want to say what you are guarding against, add a clause in the conditional: au cas où il pleuvrait.
- Does au cas où take the subjunctive?
- No, it takes the conditional, which surprises most learners. Au cas où il serait malade, not au cas où il soit malade. It is one of the very few French conjunctions that governs this mood.
- What is the difference between si and au cas où?
- Si introduces a condition the result depends on, and takes the present: si tu viens, on mangera ensemble. Au cas où introduces a contingency you are preparing for, and takes the conditional: au cas où tu viendrais, il y a de quoi manger.
- When do you use au cas où with the past conditional?
- When the possible event may already have taken place. Au cas où vous auriez déjà réglé la facture, ignorez ce rappel. The past conditional keeps the event hypothetical instead of asserting it happened.
- Is en cas de the same as au cas où?
- They cover similar ground but attach to different things. En cas de takes a noun, as in en cas de problème, appelez-nous. Au cas où takes a whole clause with a verb in the conditional, as in au cas où il y aurait un problème.