Prohibition of lex commissoria (PLC) means that before the debt is due, sides parts of agreement can not decide agree that if loan is not paid on due date ownership of the pledged property will be transferred to the creditor. PLC is regulated at the article 873/2 in Turkish Civil Code Number 4721. The purpose of the prohibition is preventing the exploitation of the debtor and preventing creditors getting unfair advantage. In study, the appearance of the PLC and its results are examined. In the first part the notion, elements and practice area of the PLC are explained. In the second part, the scope and provisions of the Prohibition are considered. In the third part, the consequences of the violation of the prohobition and the special transactions are determined. In addition, the innovations that came to Turkish Law has been stated with the Law on Movable Property Pledge in Commercial Transactions Number 6750.