This research aims to find out the legal relationships occur between sellers, buyers, and couriers in online trading transactions in e-commerce. In addition, this research also aims to determine the responsibility of the courier in online transactions if the goods sent do not arrive in accordance with the description of the items that were there initially. This research takes the background of the very rapid development of online transactions in Indonesia especially by using e-commerce. At the time this research was written, e-commerce have massively entered Indonesia, to name a few some of them are Tokopedia, Shopee, and others. Although this makes it easier for most people to make purchase and sell goods, there are still many obstacles that may occur in practice. Like many cases that happen to buyers when they make online transactions, such as cases where the item that arrive isn’t the same than what’s promised or posted on the internet or cases where items got lost in shipping. This research uses a normative research type. The data to support this thesis was obtained from a thorough search and study through books, journals, internet and information’s gained through interview. From the results of this thesis research it can be seen that there is a legal relationship between sellers, buyers and couriers. In addition, sellers, buyers, and couriers indirectly commit themselves to the existence of an electronic agreement. In cases where goods do not arrive in accordance with the initial description, the courier will be responsible in accordance with their company regulations and it will be easier if the shipment uses shipping insurance, but the courier is not responsible if the item is indeed in trouble from before shipping. The compensation will be given in the form of cash and to make arrangements that will take care of it is the seller or the e-commerce platform in question.