Comparative advertising is one of the current methods of advertising goods and services. This method has been established Based on comparing products and services in the essential characteristics such as quality, raw materials, the effectiveness of the product or external elements such as price and warranty period. Comparison can be either explicit by mentioning the name and trademark of a competitor or it can only imply the comparison with other trademark. Different approaches have been adopted in different legal systems in relation to this phenomenon because on the one hand, comparative advertising can be effective in informing consumers and protecting their rights, and on the other hand it may overshadow the rights of other competitors. At first it was the French lawyers and their jurisprudence, that according to the general rules of civil liability and prohibition of misleading advertising Law, consider the comparative advertising as an example of unfair competition and so it was prohibited and punishable. However, eventually french Laws have been reformed and the this kind of advertising – by adapting some legal requirements- became legitimate. in European ::union:: comparative advertising had a similar story and after the ban, eventually with the guidelines issued by the European authorities, in compliance with the limits and conditions set forth in the guidelines, was legitimate. In Iranian Law and Islamic jurisprudence, there is no specific rules on this matter, but according to the general rules of Islamic jurisprudence, comparative advertising can be accepted as a  legitimate method of conduct.