In short

The past conditional is the present conditional of essere/avere plus a past participle: avrei parlato, sarei andato. It does two jobs. It is the “would have” of unrealised wishes and regrets - Sarei venuto, ma ero malato (I would have come, but I was ill) - and it is the form Italian uses for the future seen from a past moment: Ha detto che sarebbe venuto (He said he would come). That second use is the one English speakers get wrong every time.

The rule

Step 1 - Build the form. Take the present conditional of the auxiliary - avrei, saresti, avrebbe, saremmo… - and add the past participle. The auxiliary is whichever one the verb already takes in the passato prossimo: avere for most verbs, essere for the movement/change-of-state group and all reflexives. With essere the participle agrees with the subject: Maria sarebbe partita, i ragazzi sarebbero partiti. Nothing here is new - it is the present conditional you learned in step 36, simply carrying a participle.

Step 2 - Job one: the unreal past (“would have”). This covers a wish that never came true, an intention that fell through, or a reproach about the past:

• Regret / unrealised wish. Avrei voluto incontrarti, ma non c’eri. I would have liked to meet you, but you weren’t there.
• Plan that failed. Sarei venuto alla festa, ma ero malato. I would have come to the party, but I was ill.
• Reproach (“should have / could have”). Avresti dovuto avvisarmi. You should have warned me. The modals dovere, potere, volere in the past conditional give English should have, could have, would have (wanted).

Step 3 - Job two: the future in the past. Here is the point learners fail. When you look at the future from a moment that is itself in the past - “he said he would come”, “I knew they would win” - Italian uses the past conditional, never the present one. English hides this because it writes both with the same word would: I would come (now) and he said he would come (reported) look identical, but Italian keeps them apart:

• A willingness now: present conditional. Dice che verrebbe volentieri. He says he would gladly come. (A plain future from now is the future: Dice che verrà.)
• Future from a past point: past conditional. Ha detto che sarebbe venuto. He said he would come.

The trigger is a reporting or thinking verb in the past - ha detto, disse, ha promesso, pensavo, sapevo, credeva. Whatever was still-to-happen at that past moment goes into the past conditional. So the live statement “Ti telefonerò” (I’ll call you), once reported after a past verb, becomes Ha detto che mi avrebbe telefonato. This is the seed of the full sequence of tenses and of reported speech.

Two extra uses, briefly. The past conditional also carries unconfirmed news about the past - Il ministro avrebbe firmato l’accordo (the minister reportedly signed the agreement) - the past twin of the hearsay conditional. And it is the main-clause verb of an impossible past hypothesis: Se avessi studiato, avrei superato l’esame (if I had studied, I would have passed) - the full pattern is step 51.

Forms & patterns

Present conditional of the auxiliary + past participle:

Present conditional (now / future) against past conditional (over and done):

The future in the past - a live future statement, reported after a past verb, shifts to the past conditional:

Examples

Common mistakes

• Ha detto che verrebbe. -> Ha detto che sarebbe venuto. A future seen from a past moment takes the past conditional, not the present one. English would hides the difference; Italian does not.
• Dovrei chiamarti ieri. -> Avrei dovuto chiamarti ieri. Should have is the past conditional of dovere. The present conditional dovrei can only mean I should (now), never I should have.
• Avrei andato al mare. -> Sarei andato al mare. The auxiliary is the one the verb takes in the passato prossimo. Andare takes essere, so it is sarei andato, never avrei andato.
• Maria sarebbe partito. -> Maria sarebbe partita. With essere the participle agrees with the subject, exactly as in the passato prossimo: feminine singular partita.
• Ha promesso che mi aiutava. -> Ha promesso che mi avrebbe aiutato. A promise about the future, reported from the past, is not the imperfect - it is the past conditional.

Tips

• Two English signals point straight to this form. (1) would have + verb (a regret or unreal past): avrei fatto. (2) would + verb after a past reporting verb like he said / I thought / she knew (the future in the past): sarebbe venuto. Spot either signal and reach for the past conditional.
• Should have, could have, would have = avrei dovuto / avrei potuto / avrei voluto. These three chunks are among the most useful things a B2 speaker owns; learn them as ready-made phrases rather than rebuilding them each time.
• This is where Italian parts company with English - and with French and Spanish. Those languages keep the present conditional for the future in the past (il a dit qu’il viendrait, dijo que vendría). Italian insists on the past conditional (Ha detto che sarebbe venuto). If you speak French or Spanish, this is the exact habit to unlearn.
• Same auxiliary rules as always. Auxiliary choice, irregular participles and essere-agreement are imported unchanged from the passato prossimo; the only moving part is that avere/essere now sit in the present conditional (avrei, sarei).