Short answer. It is voidable. Article 1328 of the Civil Code specifically states that contracts agreed to during a hypnotic spell are voidable — not void and not automatically binding. This means the contract exists and may be enforced unless you take action to have it annulled within the period allowed by law.
What the law says
Contracts agreed to in a state of drunkenness or during a hypnotic spell are voidable.
Civil Code, Article 1328 — Lucid Intervals; Drunkenness; Hypnosis. Read the full provision →
What 'voidable' means and why it matters
A voidable contract is not automatically without effect — it has legal existence and can even be ratified and made fully binding. The word 'voidable' means it is capable of being annulled at the option of the injured party, but only if that party acts to challenge it. Until annulment is sought and granted, the contract stands. This is different from a void contract, which has no legal effect from the start and cannot be ratified by anyone. Article 1328 places hypnosis-induced contracts in the middle ground: defective but not automatically null.
Why hypnosis affects consent
The underlying rationale for Article 1328 is consent. A valid contract requires genuine, free, and informed consent from both parties. Someone under a hypnotic spell has impaired or suspended voluntary control — they may be responsive and cooperative but not fully exercising their rational will. This removes genuine consent. The law does not treat the contract as void, perhaps because the hypnotic state is temporary and the injury may be remediable, but it does give the affected party a remedy to undo the contract.
How to challenge the contract
To have the contract annulled, you would need to establish two things: first, that you were in a hypnotic state at the time of signing, and second, that the contract was entered into during that spell. Evidence is central: witness accounts of the circumstances, records of who induced the hypnosis and under what conditions, and any communications or facts showing you had no rational awareness of what you were agreeing to. Once annulled, the parties must restore to each other what was received under the contract. Failing to seek annulment within the applicable period — or ratifying the contract afterward — can make it binding.
Ratification: when the contract becomes valid anyway
Because the contract is voidable rather than void, it can be ratified. If you later become aware of the contract's contents and, with full knowledge, voluntarily comply with it or confirm it — whether in writing or by conduct — you may lose the right to challenge it. The contract you originally could not freely consent to becomes binding through your subsequent free affirmation. This is why acting quickly matters: do not continue performing under a contract you believe was signed under hypnosis, as continued compliance may be read as ratification.