Well-known marks have been a controversial topic for any subject in the legal area. Up until now, there has never been any binding legal document that states the criteria for a trademark to be considered as a well-known mark. Legal experts have issued concepts regarding well-known marks, but none have attempted to states the requirements for a well-known mark. Before the newest addition to the law regarding Trademarks in Indonesia was issued, Law No. 15 Year 2001 on Trademarks became the sole binding regulation in Indonesia if any law subject would conduct activities related to trademarks rights. The legislative body regulated well-known marks only in one of the provision, which would be the Explanation for Article 6 (1) letter b. The requirements for a trademark to be considered as a well-known mark are the following: (1) the general public’s knowledge on that said trademark in the particular field it is classified in, (2) the reputation of the well-known mark that is achieved from intense and widespread promotion of said trademark, (3) the investment used by in some countries that are invested by the owner, and (4) evidence that the said trademark is registered in some countries. Even though the legislative body in Indonesia issued this regulation, problems that surfaced from the very broad interpretation of each requirement is not a rare thing to occur in the implementation in court. Judges and even legal experts in Indonesia still has not produced interpretations that would narrow down all of the requirements for a well-known mark, most only discussed one or two requirements. In court proceedings, the plaintiff and the respondent may bring upon the panel of judges the evidences that would suffice their arguments. However, the court decision will ultimately come to a conclusion based on each of the Judge’s belief.