In contractual relations arising from sales, one of the significant and contentious challenges is the third-party claim to the subject matter of the sale-claims that may take the form of ownership or other real rights thereby disrupting the buyer’s use and enjoyment and potentially breaching the seller ob ligation.

This treatise, employing and analytical – comparative approach examines claims of third parties to the subject matter of the sale and the guarantee of their implementation in Imami jurisprudence and Iranian law and international sale convention (1980 vienna) and English law.

Under Iranian law, if a third party has a claim for ownership of the subject matter of the sale or if the third party makes another claim and is proven, guarantee for voiding the exchange and refund and damage claims have been predicted for the buyer his damage also includes one due to decrease in benefit .

 In English law and the Convention, in these cases, the buyer with good faith can take action in accordance with the existing conditions and claim damages bused on the price on the day of disposal.

The aim of this thesis is to analyze and compare cases and examples of third-party claims and by the mentioned enforceable guarantee, the common points and difference of the legal systems of Iran and UK and International Sales Convention would be studied, and present some solutions to improve the efficiency of protecting the buyer in similar cases.

Research findings show that the Convention and English law have more explicit and more legal perspectives in most cases in order to protect the buyer, but Iranian law is concentrated mostly on the general rules of contractual liability and the implementation of traditional accomplishments, some suggestions are presented to reform domestic rules and alignment with international rules.