Almost every English speaker learning Spanish translates 'when' as 'cuando' — and then freezes when they have to pick a verb form.
Here is the sentence that trips people up: 'Llámame cuando llegas.' To an English ear this sounds fine. In Spanish, it means 'Call me every time you arrive (as a habit).' If you want to say 'Call me when you get here' — one future occasion — Spanish needs the subjunctive: Llámame cuando llegues. Same English sentence. Two completely different Spanish meanings.
The governing rule: cuando + event that has already happened or happens habitually → indicative. Cuando + event that has not happened yet → present subjunctive. The time frame of the event in the cuando clause — not the main verb — decides the mood.
This distinction does not exist in English. English uses 'when' identically for past events, habits, and future plans without touching the verb form. Spanish embeds the distinction in the verb itself. Until that clicks, learners default to the indicative every time and produce sentences that are either ambiguous or quietly wrong for the future.
Why English Speakers Get This Wrong
Think about how English handles the word 'when.' It is completely flexible: 'When I was young, I played football' (past). 'When she calls, I always answer' (habit). 'When you arrive, text me' (future). The subordinate clause after 'when' stays in a present-like tense regardless of the time reference. English relies on context and adverbs — 'When you arrive tomorrow' — to make the future reading clear. The verb form itself does not change.
Spanish refuses to leave this ambiguous. If the event inside the cuando clause is still upcoming — not yet real, not yet confirmed — Spanish reaches for the present subjunctive. The subjunctive is the mood of the not-yet-certain. As soon as the action lands in the past or establishes itself as a regular fact, it moves to the indicative, the mood of the known and the real.
The Single Test That Decides Everything
Has this event already happened, or does it happen regularly? → Indicative. Is this event still pending — in the future, not yet realized? → Present subjunctive. The timeline of the event inside the cuando clause is the deciding factor, not the main verb.
This test is different from the trigger-based approach to the subjunctive, where you memorize lists of verbs — querer que, dudar que, esperar que — that force the subjunctive. With cuando, you are not scanning the main verb for a magic word. You are simply asking: is this event real yet?
Real and habitual actions belong to the indicative's world of observable facts. Pending future actions belong to the subjunctive's world of the projected and the possible. The mood signals which world the action currently inhabits.
| Cuando + indicative (real / habitual) | Cuando + subjunctive (future / unrealized) |
|---|---|
| Cuando llega el tren, subo. (habit — I always board) | Cuando llegue el tren, subiré. (future — when it arrives, I'll board) |
| Cuando era niño, jugaba al fútbol. (past — I used to play) | Cuando sea mayor, jugaré al fútbol. (future — when I grow up, I'll play) |
| Cuando habla, todos escuchan. (habit — when she speaks, all listen) | Cuando hable en la reunión, todos escucharán. (future — when she speaks, they will listen) |
| Cuando llegué a casa, estaba cansado. (past — I arrived and was tired) | Cuando llegue a casa, descansaré. (future — when I get home, I'll rest) |
| Sé cómo se siente cuando trabaja demasiado. (habit) | Te avisaré cuando sepa algo. (future — when I find out, I'll tell you) |
Habitual Actions: Always Indicative
When the cuando clause describes something that happens repeatedly — a regular pattern, a standing routine — Spanish uses the present indicative. These events are facts. They happen. The indicative reports known reality, and recurring actions are part of known reality.
- Cuando como, no hablo. (When I eat, I don't talk. — Always. Every time.)
- Cuando mi jefe llama, siempre respondo. (When my boss calls, I always answer.)
- Cuando hace frío, me pongo el abrigo. (When it's cold, I put my coat on.)
- Cuando vienes a verme, siempre me alegras el día. (When you visit, you always brighten my day.)
Past Events: Always Indicative
Past events are real by definition — they have already happened and entered the world of fact. Spanish always uses the indicative for past cuando clauses, whether a single completed event (preterite) or an ongoing past situation (imperfect).
- Cuando llegué, ya habían comido. (When I arrived, they had already eaten.)
- Cuando era niño, vivía en Sevilla. (When I was a child, I lived in Seville.)
- Cuando la vi, me puse nervioso. (When I saw her, I got nervous.)
- Cuando terminamos el proyecto, lo celebramos con una cena. (When we finished the project, we celebrated with dinner.)
The choice between preterite and imperfect in past cuando clauses follows the normal preterite/imperfect logic — a completed event versus a background situation — and has nothing to do with the subjunctive. The mood stays indicative in either case.
Future / Unrealized Events: Present Subjunctive
This is where learners stumble most often. In English, 'When I get there...' uses a present-tense verb even though the arrival is clearly in the future. Spanish marks that future status explicitly with the present subjunctive. The action is still unrealized — it has not happened — and the subjunctive is Spanish's signal for exactly that.
Critical rule: never place the future tense directly after cuando. 'Cuando llegaré' is a calque from English ('when I will arrive') and is ungrammatical in Spanish. Use the present subjunctive: 'Cuando llegue.' This rule holds without exception — no matter what tense the main clause uses.
- Cuando llegues a Madrid, llámame. (When you get to Madrid, call me.)
- Te lo diré cuando sepa algo. (I'll tell you when I know something.)
- Cuando tengas tiempo, hablamos. (When you have time, let's talk.)
- Avisadme cuando terminéis. (Let us know when you all finish.)
- Podrás salir cuando hayas terminado los deberes. (You can go out when you've finished your homework.)
- Cuando sea mayor, quiero ser médico. (When I grow up, I want to be a doctor.)
Other Temporal Conjunctions That Follow the Same Rule
The realized/unrealized distinction is not exclusive to cuando. Several other temporal conjunctions work with the same logic: past and habitual reference takes the indicative; future reference takes the present subjunctive. Recognizing this saves you from treating each conjunction as a separate rule to memorize.
| Conjunction — past / habitual example (indicative) | Future / unrealized example (subjunctive) |
|---|---|
| en cuanto (as soon as) — En cuanto llega, se pone a trabajar. (habit) | En cuanto llegue, me llama. (future) |
| hasta que (until) — Esperé hasta que llegó. (past — until she arrived) | Espera hasta que llegue. (future — wait until she arrives) |
| mientras (while) — Mientras comía, veía la tele. (past) | Llámame mientras esperes. (future — while you wait) |
| después de que (after) — Después de que llegó, hablamos. (past) | Después de que llegue, hablaremos. (future) |
| antes de que (before) — Lo limpié antes de que llegara. (past — always subjunctive) | Termínalo antes de que llegue. (future — always subjunctive) |
Special Case: Antes de que Always Takes the Subjunctive
'Before' (antes de que) takes the subjunctive even in past reference. The logic: 'before' always refers to something that hadn't happened yet at the moment of reference — so even in the past, the 'before' event was technically unrealized from the perspective of the main action. This makes antes de que a reliable, exception-free subjunctive trigger.
- PAST: Lo limpié antes de que llegara. (I cleaned it before she arrived. — imperfect subjunctive llegara)
- FUTURE: Termínalo antes de que llegue. (Finish it before she arrives. — present subjunctive llegue)
Three Mistakes to Stop Making
Mistake 1: Putting the Future Tense After Cuando
✗ Cuando llegarás, llámame. → ✓ Cuando llegues, llámame. | ✗ Te lo diré cuando sabré. → ✓ Te lo diré cuando sepa. | The future tense directly after cuando is ungrammatical in standard Spanish. Always use the present subjunctive for future reference.
This error is a direct calque from English ('When you will arrive...'). Even learners who know the subjunctive rule fall back on the future tense under pressure because English conditions them to express futurity with future verb forms. Train yourself to notice which tense you are reaching for and redirect to the subjunctive.
Mistake 2: Using the Present Indicative for Future Events
Using the present indicative after cuando when you mean a future event is tempting because English does it — 'When you arrive' is present tense in English, and so is the corresponding Spanish form 'cuando llegas.' But in Spanish, 'cuando llegas' means 'every time you arrive' — a habitual pattern. For a single, one-time future arrival, you need the subjunctive: 'Cuando llegues.' The indicative collapses a future statement into a habitual one.
Mistake 3: Confusing Cuando and Si
When learners discover that si (if) + hypothetical uses the imperfect subjunctive, they sometimes misapply that pattern to cuando. The two conjunctions work very differently in the subjunctive.
| Cuando | Si |
|---|---|
| Future events: present subjunctive (cuando llegue) | Hypothetical: imperfect subjunctive (si llegara) |
| Past / habitual: indicative (cuando llegó / cuando llega) | Open real condition: present indicative (si llega) |
| Conditional? Never — use future or present subjunctive | Conditional? Never — see si clause rules |
| Temporal clause: when X, then Y | Conditional clause: if X, then Y |
The key difference for future reference: cuando venga (present subjunctive); si viniera (imperfect subjunctive). Using 'cuando viniera' sounds literary or archaic in most everyday contexts. Using 'si venga' is simply wrong. The two conjunctions are not interchangeable, and their subjunctive tenses are different.
A Quick Decision Checklist
When you are mid-sentence and not sure which form to use after cuando, run through these four checks in order:
- Is the cuando event already in the past? → Indicative (preterite for single completed events, imperfect for background situations). 'Cuando llegué...' / 'Cuando era niño...'
- Does the cuando event happen regularly or habitually in the present? → Present indicative. 'Cuando llega...' / 'Cuando como...'
- Is the cuando event still in the future — pending, unrealized, not yet confirmed? → Present subjunctive. 'Cuando llegue...' / 'Cuando sepa...'
- Is the conjunction antes de que? → Always subjunctive regardless of time (imperfect subjunctive for past reference, present subjunctive for future). No exceptions.
Practice: Indicative or Subjunctive After Cuando?
Practice 1
When she arrives (future), I'll tell her the news.
Cuando llegue, le diré la novedad.
Future, unrealized → present subjunctive llegue. Not llegará (future after cuando is wrong) and not llega (present indicative would mean a habitual pattern, not a single future event).
Practice 2
When I was a student (past), I lived in a shared flat.
Cuando era estudiante, vivía en un piso compartido.
Past ongoing situation → imperfect indicative era and vivía. Past reality confirmed: no subjunctive needed.
Practice 3
Call me as soon as (en cuanto) you know something (future).
Llámame en cuanto sepas algo.
Future reference after en cuanto → present subjunctive sepas. The same realized/unrealized rule applies to en cuanto as to cuando.
Practice 4
Every time she calls (habitual), I'm busy.
Cuando llama, estoy ocupado.
Habitual, recurring event → present indicative llama. Not a single future event, so no subjunctive.
Practice 5
Finish it before she arrives (future).
Termínalo antes de que llegue.
Antes de que always takes the subjunctive regardless of time frame. Present subjunctive llegue for this future reference.
Practice 6
When I have time (future), I'll learn to cook Spanish food.
Cuando tenga tiempo, aprenderé a cocinar comida española.
Future, unrealized → present subjunctive tenga. Never 'cuando tendré' — the future tense directly after cuando is always wrong.
Quick-Reference Summary
| Situation — mood / tense | Example |
|---|---|
| Past completed event → indicative preterite | Cuando llegué, vi el mensaje. |
| Past background / ongoing → indicative imperfect | Cuando era joven, corría cada mañana. |
| Habitual / recurring present → indicative present | Cuando llueve, me quedo en casa. |
| Future / unrealized (any main-clause tense) → present subjunctive | Cuando llegues, dime. / Cuando sepa, te llamo. |
| Antes de que (any time reference) → always subjunctive | Antes de que salgas, cierra la puerta. |
Where to Go Next
The cuando rule is part of a larger map of when Spanish chooses the subjunctive. For the complete list of all the words and phrases that trigger it — from querer que to para que to a menos que — with full usage notes and examples, see the subjunctive triggers guide at /blog/subjunctive-triggers-spanish-guide/. For the si clause system — where three conditional types each use a different set of tenses — the companion post is at /blog/si-clauses-spanish-conditionals/. The present subjunctive forms you need for cuando + future are covered step by step at /tenses/presente-de-subjuntivo/.
MuyVerbs quizzes all subjunctive forms — including the present subjunctive — across a library of 3,015 Spanish verbs. The quiz at /quiz-plus/ lets you drill by tense until the subjunctive becomes automatic. If you are building a structured study plan, the learning path at /learning-path/ shows exactly where the subjunctive fits and what to practise before and after it.
Does 'cuando' always take the subjunctive in Spanish?
No. When the cuando clause refers to a past event or a habitual action, use the indicative: 'Cuando llegué, te vi' (past) or 'Cuando llueve, me quedo en casa' (habit). Use the present subjunctive only when the event is still in the future or has not yet happened: 'Cuando llegues, llámame.' The time frame of the event in the cuando clause is what decides the mood.
Why can't I use the future tense after 'cuando' in Spanish?
Spanish grammar prohibits the future tense directly after cuando. Instead, use the present subjunctive for future reference: 'Cuando llegue' (not 'cuando llegará'). This differs from English, where 'will' sometimes appears even in subordinate 'when' clauses. The present subjunctive covers the entire notion of future-and-unrealized after temporal conjunctions in modern Spanish.
What is the difference between 'cuando viene' and 'cuando venga'?
'Cuando viene' uses the present indicative and describes a habitual, recurring action: every time she comes (as she regularly does), we talk. 'Cuando venga' uses the present subjunctive and describes a single, still-unrealized future event: when she comes this time (which hasn't happened yet), we will talk. Same conjunction, opposite mood, different time frame.
Do other temporal conjunctions follow the same rule as 'cuando'?
Yes. En cuanto (as soon as), hasta que (until), mientras (while), and después de que (after) all take the indicative for past and habitual reference and the present subjunctive for future reference. Antes de que (before) is the exception: it always triggers the subjunctive regardless of time, because 'before' inherently refers to something that hadn't yet happened at the moment of reference.
What is the difference between 'cuando' + subjunctive and 'si' + subjunctive?
When expressing future events, cuando uses the present subjunctive ('cuando llegue'), while si with a hypothetical condition uses the imperfect subjunctive ('si llegara'). The conjunctions serve different purposes: cuando marks temporal sequence (when X, then Y), while si marks conditional dependency (if X, then Y). The two subjunctive forms are not interchangeable after their respective conjunctions.
Can I use 'cuando' with the imperfect subjunctive?
In modern spoken Spanish, cuando + imperfect subjunctive sounds literary or archaic. You may encounter 'cuando llegara' in formal writing or older literature. In everyday speech, current Spanish uses 'cuando llegó' (indicative) for past events and 'cuando llegue' (present subjunctive) for future events. Avoid the imperfect subjunctive after cuando unless you are writing formally.
How do I form the present subjunctive needed after 'cuando'?
Take the yo form of the present indicative, drop the -o, and add subjunctive endings: -e/-es/-e/-emos/-éis/-en for -AR verbs, -a/-as/-a/-amos/-áis/-an for -ER/-IR verbs. Examples: hablar → hablo → habl- → hable; comer → como → com- → coma; venir → vengo → veng- → venga. Irregular yo forms carry into the stem: tener → tengo → teng- → tenga; ser → soy → se- → sea; ir → voy → vay- → vaya.