Modernization has introduced a new form of trading which is online marketplace transactions. In an online marketplace transaction, there are three parties involved which are the buyer, seller, and online transaction platform provider called a marketplace. Marketplaces are a new form of online transaction innovation in which it eases buying and selling transactions. However, with all those advancements, comes new legal issues where new legal stance/perspectives are needed in order to help protect one’s rights in the case it was violated. The research method used for this study is normative juridical research. Normative juridical research is research aimed only at written regulations which is closely related to the library, because the research will require secondary data from the library. The types of data that will be used in this research are primary, secondary, and qualitative data. The goal of this research is to identify how a marketplace is responsible for a transaction which causes the consumer to be at a loss, and to analyse consumer protection acts that are implemented by Marketplace Tokopedia. The first result of this research is analysing how the online marketplace is responsible if a seller sold a product/service that was not in accordance with how it was advertised. The second result of this research is analysing what consumer protection protocols are implemented in the online marketplace.