When a Brazilian talks about something that will happen "when" something else happens, the sentence splits cleanly into two halves that take different verb forms. The subordinate half — the "when" clause — uses the future subjunctive (futuro do subjuntivo). The main half uses whatever ordinary future-marking strategy the speaker likes. English collapses both halves into the present tense ("When you arrive, I'll call you"), which is exactly why this is so hard for English speakers: you have to learn to put a special verb form into a clause where your native language puts nothing special at all.
The two halves of a future sentence
Take the everyday sentence "When you arrive, I'll call you." A Brazilian says:
Quando você chegar, eu vou te ligar.
When you arrive, I'll call you.
Look at the two verbs. In the quando clause, the verb is chegar — but that is not the infinitive sitting there doing nothing. For chegar, the future subjunctive happens to be identical to the infinitive (chegar). In the main clause, the verb is vou ligar — the periphrastic future (ir + infinitive), the form Brazilians reach for in almost all everyday future talk.
The rule, stated plainly:
- Subordinate clause introduced by a future-time conjunction → future subjunctive.
- Main clause → any future-marking strategy (periphrastic vou fazer, simple future farei, or even the present used for the future).
Why the subordinate clause is subjunctive at all
English speakers reasonably ask: the arrival will happen, so why a subjunctive — the mood of doubt and wishes? The answer is that at the moment of speaking, the arrival has not yet happened. It is a projected, not-yet-real event. The future subjunctive is precisely the form Portuguese uses to flag "this event is anticipated but unrealized." You are not asserting that you arrived; you are pointing at a future condition and saying "whenever that becomes true, the main thing follows."
This is the same logic as the present and imperfect subjunctive — non-fact, non-asserted — applied to the future timeline. Spanish once had this future subjunctive too (cuando llegares), but it died out and Spanish now uses the present subjunctive (cuando llegues). Portuguese kept it alive, and in Brazil it is fully active in everyday speech.
Assim que eu souber de algo, te aviso.
As soon as I know something, I'll let you know.
Enquanto você estiver no trânsito, vou adiantando aqui.
While you're stuck in traffic, I'll get started here.
The main clause is free — five strategies
Because the main clause picks its own form, you will hear all of these, all correct:
| Main-clause strategy | Example | Register |
|---|---|---|
| Periphrastic future (ir + inf.) | Quando ela chegar, vou abrir o vinho. | (informal) — the default |
| Present for future | Quando ela chegar, abro o vinho. | (informal) |
| Simple future | Quando ela chegar, abrirei o vinho. | (formal) |
| Imperative | Quando ela chegar, abra o vinho. | (neutral — an instruction) |
| Modal / obligation | Quando ela chegar, tenho que abrir o vinho. | (neutral) |
Five complete bi-clausal examples
Quando o pedido chegar, eu te mando uma foto.
When the order arrives, I'll send you a photo.
Depois que você terminar a prova, a gente almoça junto.
After you finish the exam, we'll have lunch together.
Assim que der, eu te ligo de volta.
As soon as I can, I'll call you back.
Se você quiser, a gente pode ir de carro.
If you want, we can go by car.
Enquanto vocês esperarem na fila, eu pego os ingressos.
While you wait in line, I'll grab the tickets.
Notice the verb pairs: chegar / mando, terminar / almoça, der / ligo, quiser / pode, esperarem / pego. The first verb of each pair is future subjunctive; the second is an ordinary indicative or periphrastic future. (Der is the future subjunctive of dar, quiser of querer, esperarem the third-person-plural future subjunctive of esperar.)
The "quando" magic-word effect
For future events, quando is almost a trigger word: when it introduces a clause about something that hasn't happened yet, the future subjunctive follows it the overwhelming majority of the time. If you train yourself to feel "quando + future event → chegar / for / tiver / puder," you will be right far more often than not. The same reflex extends to the whole family of future-time conjunctions: assim que (as soon as), depois que (after), enquanto (while), logo que (as soon as), sempre que (whenever), até que (until).
Sempre que você precisar, é só me chamar.
Whenever you need to, just give me a shout.
The one big exception: habitual past
There is exactly one common situation where quando does not take the future subjunctive, and it trips up learners constantly: when quando describes a repeated, habitual action in the past. Then both verbs go in the imperfect indicative, because nothing is being projected into the future — you are narrating a routine that used to happen.
Quando eu chegava em casa, ela me cumprimentava na porta.
When(ever) I got home, she would greet me at the door.
Here chegava and cumprimentava are imperfect indicative — "I used to arrive, she used to greet." Compare the future version, which uses the future subjunctive:
Quando eu chegar em casa, ela vai me cumprimentar na porta.
When I get home, she'll greet me at the door.
The split is about timeline and reality, not about the word quando itself:
- Quando
- repeated past habit → imperfect indicative (real, repeated, completed routine).
- Quando
- unrealized future event → future subjunctive (projected, not-yet-real).
- Quando
- a single completed past event → preterite (Quando ela chegou, abri o vinho — "When she arrived, I opened the wine").
Common Mistakes
The errors below are the ones English speakers make almost without fail, because English uses the present tense in the "when" clause.
❌ Quando você chega, eu vou te ligar.
Incorrect — present indicative 'chega' calques English 'when you arrive'.
✅ Quando você chegar, eu vou te ligar.
When you arrive, I'll call you.
❌ Quando você vai chegar, eu te ligo.
Incorrect — this turns the 'when' clause into a question-like future; not how the time clause works.
✅ Quando você chegar, eu te ligo.
When you arrive, I'll call you.
❌ Assim que eu sei de algo, te aviso.
Incorrect — present 'sei'; the knowing is still in the future.
✅ Assim que eu souber de algo, te aviso.
As soon as I know something, I'll let you know.
❌ Quando eu chegar em casa, ela me cumprimentava.
Incorrect — mixes a future-subjunctive 'when' clause with a past-habit main verb.
✅ Quando eu chegava em casa, ela me cumprimentava.
When I got home, she would greet me. (habitual past — both imperfect)
❌ Depois que você terminará, a gente almoça.
Incorrect — synthetic future 'terminará' cannot follow 'depois que'; the time clause needs the future subjunctive.
✅ Depois que você terminar, a gente almoça.
After you finish, we'll have lunch.
Key Takeaways
- A future sentence has two halves. The time clause (introduced by quando, assim que, depois que, enquanto…) takes the future subjunctive. The main clause takes any future strategy — usually vou + infinitivo or the present.
- The future subjunctive marks the event as anticipated but not yet real, which is why English's plain present has no equivalent here.
- Quando is a near-automatic future-subjunctive trigger for future events.
- The single big exception: quando
- a repeated past habit uses the imperfect indicative in both clauses, not the subjunctive.
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Start learning Portuguese→Related Topics
- Futuro do Subjuntivo: FormationA2 — How to build the future subjunctive in Brazilian Portuguese — derived from the third-person plural preterite, and why it looks deceptively like the infinitive.
- Futuro do Subjuntivo: UsageA2 — When to use the future subjunctive in Brazilian Portuguese — the obligatory form after 'quando', 'se', 'enquanto', 'assim que' and other time conjunctions pointing to the future.
- Conjunctions of Time + SubjunctiveB1 — Temporal conjunctions like quando, assim que and antes que that govern the future subjunctive for future events — and the outlier antes que, which always takes the subjunctive.
- The Periphrastic Future (vou + infinitive)A1 — How Brazilians actually talk about the future: ir in the present plus an infinitive.
- Imperfeito for Habitual PastA2 — Using the imperfect to express what used to happen — repeated, habitual, or customary actions in the past.