Short answer. Yes. Article 2091 provides that a pledge or mortgage may secure all kinds of obligations — whether pure, or subject to a suspensive or resolutory condition. So a debt that depends on a future uncertain event can be validly secured, though what the creditor can enforce tracks whether and how the condition operates.
What the law says
The contract of pledge or mortgage may secure all kinds of obligations, be they pure or subject to a suspensive or resolutory condition.
Civil Code, Article 2091 — Obligations That May Be Secured. Read the full provision →
Security follows the principal obligation
A pledge or mortgage is an accessory contract: it does not stand on its own but exists to secure a principal obligation. Article 2091 confirms how wide that principal may be: The contract of pledge or mortgage may secure all kinds of obligations, be they pure or subject to a suspensive or resolutory condition. A debt need not be presently due and unconditional to be secured. An obligation that hinges on some future, uncertain event can be backed by collateral from the outset, with the security taking its character from the obligation it serves.
Suspensive and resolutory conditions
The two kinds of condition work in opposite directions. A suspensive condition holds the obligation in suspense: it arises and becomes demandable only if the event happens. A resolutory condition does the reverse: the obligation exists and is effective now, but it is extinguished if the event occurs. Article 2091 allows a pledge or mortgage to secure a debt of either type. The collateral can be put in place at the start, ready to answer for the obligation whether it is waiting to arise or already in force but liable to end.
What the creditor can enforce, and when
Because the security is accessory, its enforceability moves with the principal debt. Where the condition is suspensive, the creditor cannot yet foreclose on a debt that has not become demandable; the pledge or mortgage sits in place until the condition is fulfilled and the obligation matures. Where the condition is resolutory, the debt is enforceable in the meantime, but if the event occurs and extinguishes the obligation, the security falls with it — there being no principal left for it to secure. The state of the condition therefore governs when, and whether, the creditor may realise on the collateral.
Draft the condition with care
Since so much turns on the condition, spell it out precisely in the documents: what event triggers it, how and when it is deemed fulfilled, and what becomes of the obligation as a result. Both parties should be clear that the creditor's ability to enforce the pledge or mortgage depends on the principal obligation being live and demandable at the time. And remember the accessory nature of the security: if the condition means no principal obligation ever arises, or extinguishes one that did, there is correspondingly nothing for the pledge or mortgage to enforce.