Short answer. No. Article 1549 of the Civil Code is explicit: the buyer does not need to appeal the decision in order for the seller to become liable for eviction. You can let a judgment against you become final and still proceed against your seller — no appeal is required as a condition for that claim.
What the law says
The vendee need not appeal from the decision in order that the vendor may become liable for eviction.
Civil Code, Article 1549 — No Need to Appeal. Read the full provision →
What eviction means in sales law
In property law, "eviction" in the context of a sale does not only mean being physically removed from a house. It refers to the legal concept of being deprived of the thing purchased — or of a part of it — by a final judgment in favor of someone who has a better right to the property. If you bought land and a third party successfully sues you and a court orders you to give up the property or part of it because that third party has a prior and superior right, that is eviction in the legal sense. The seller's warranty against eviction is the promise that you will not be disturbed in your ownership in this way.
The rule: no appeal needed
When you lose the ejectment or ownership case and a court deprives you of what you bought, you might wonder: should I appeal first? Maybe the appeals court will reverse the decision. Article 1549 removes that requirement. The buyer does not need to exhaust the appeals process before claiming against the seller for eviction. You can accept the judgment, comply with it, and then turn to your seller and demand indemnity. The seller's liability is not conditional on you having fought the case all the way up the appellate ladder.
What the seller owes when eviction occurs
When eviction happens, the seller's warranty covers more than just refunding the purchase price. The Civil Code's provisions on eviction also contemplate recovery of fruits, costs of the suit, expenses, and damages in proper cases. The exact scope depends on the circumstances, including whether the seller acted in good faith or bad faith. The key point here is that Article 1549 removes a procedural barrier — the buyer does not need to appeal — but the full picture of what you can recover from the seller involves other provisions in the same chapter of the Civil Code.
Practical takeaway
If you lost a case and you were evicted from property you bought — meaning a court upheld someone else's superior right over what you purchased — you do not have to appeal that case as a prerequisite to going after your seller. You may still choose to appeal if you believe the decision is wrong, but your right to hold the seller liable is not contingent on it. The law is designed so that the buyer is not trapped into years of litigation just to preserve a warranty claim.