A research regarding bad faith implementation as a reason for a brand cancellation according to the Law No. 15 of 2001 is intended to find out the existence of similarity implementation in principle and bad faith in a lawsuit of a brand registration cancellation. Cases taken between Aqua against Aqualiva, which is Aqua is a well known brand. Aqualiva has violated the provisions of Article 4 and 6 according to the Laq No. 15 of 2001. This research is a normative research, research based on literature, which are secondary data. Supported with researches on decisions of a Commercial Courts concerning bad faith and similarity implementation in principle in a lawsuit of a brand registration. Based on Article 4 and 6 of the Law No. 15 of 2001, a brand cannot be registered if it is based on bad faith. This case was brought up to the level of appeal for Aqua does not accept that their trademark is not considered as a well-known brand. In the end, Aqua won the case and requested to cancel Aqualiva brand through the Directorate of Intellectual Propery Rights.