Blockchain technology is essentially a registry that records data in encrypted form; which is not kept by a central organization; and where all the information in encrypted form is shared with every participant in the system. The transactions carried out in this register are recorded in blocks which are linked to each other and each new transaction must be kept unchanged with the information of the previous transactions in order to be approved. For this reason, blockchain technology is considered to be a technology that eliminates intermediary institutions, offers equal opportunities to every participant and is almost impossible to manipulate. The digital currency referred to as Bitcoin is based on this technology, but blockchain technology is not limited to this. The trust established by intermediary institutions such as banks and various governmental institutions is replaced in this system by the fact that each participant has knowledge about each transaction and thus can personally check whether the transaction is real or not. In terms of private enterprises, especially in the banking, transportation and production sectors, but also in the public sector such as land registry, population or health services, it is hoped that this technology will lead to more efficiency. However, there is no uniform appearance to blockchain technology. On the contrary, the networks that can be established as open or closed to the public and the approval of the transactions may differ in terms of time and the persons who are entitled to approve block/transactions. Smart contracts, which provide a framework for transactions in the blockchain network, allow system participants to make many different transactions among the group by simply going beyond crypto currency transactions. There are many different aspects of this kind of contracts which can provide great convenience to the parties and save time, especially during the execution of the contracts. While money transfers constitute the simplest of these transactions, other transactions are more complex - a loan agreement or a real estate sale can be realized within the same transaction or networks where autonomous vehicles automatically deliver products to the network participants can be established with charging stations and distribution systems which can operate autonomously. However, blockchain technology is based on the principle that the transaction history cannot be changed and the smart contracts associated with this technology also bring many problems in terms of data protection law and law of obligations. First of all, an answer should be sought in the blockchain network about how to conclude a contract, when will it be established, and when will it come into effect. In particular, the so-called fork blocks that are not accepted gain importance in this context. In a currently established contract, there are different possibilities such as the cancellation, adaptation and withdrawal of contracts if one of the parties’ wills is disabled. In addition, in terms of those contracts concluded by the restricted, our legal order stipulates various regulations. In all these cases, although a valid transaction may appear in the blockchain network, the legal order will void this transaction. Therefore, a discrepancy between the legal situation and the blockchain network will occur. At the stage of the execution of the contracts, our legal order has placed the interests of one party above the interests of the other party in various examples. If the execution of contracts is carried out automatically, these protection mechanisms will be disabled. The fact that a transaction in the past cannot be changed in any way may also contradict the Law on the Protection of Personal Data. In this context, although it is open to debate whether personal data is in question or not, the right of the person concerned to request the deletion of personal data will be impossible if this question is answered positively. This will require the deletion of the corresponding process in the entire network, which will cause the block chain to ‘break’. The question of how the right to be forgotten, which has been the subject of discussion in recent years, can be applied within the framework of this technology also raises questions. The identification of the data controller in the blockchain network is also an important problem. Within this framework, there are different actors such as the programmer of the network, the participants, the actors who determine the conditions of participation in the network and also miners. It will be necessary to determine which of these actors are responsible for the processing of personal data. The aim of this study is to evaluate block-chain technology in terms of our current legal order, especially in terms of data protection law and the law of obligations.