Besides the unilateral freely revocable testamentary will, the second form of testamentary dispositions is the contract of inheritance. The contract of inheritance is on the one hand a form of testamentary disposition, and on the other hand a contract. Due to its nature, the inheritance contract is also referred to as a contract with dual character. By means of its binding character, the contract of inheritance constitutes a substantial alternative to the testamentary will. Taking into consideration the testator’s private autonomy in terms of private law, it is worth examining the significance of the binding effect of the contract of inheritance. The Turkish Civil Code Art. 527/1 states that the testator, by means of a contract of inheritance, commits to bequeath his estate or legacy to the other contracting party or IV a third party. This is the legal definition of the positive inheritance contract. These are the two main types of inheritance contracts, whereby the principle of numerus clausus does not apply. According to Art. 527/2 (ZGB Art. 494/2), the testator may freely dispose of his assets despite the concluded inheritance contract. However, testamentary dispositions or gifts that conflict with the obligations under the contract of inheritance are challengable. The binding effect of the contract of inheritance described in Art. 527/ 2 is highly controversial, and thus there are different opinions in literature and case law. The Turkish Civil Code Art. 527 is the translation of Art. 494 of the Swiss Civil Code. Therefore, this dissertation focuses primarily on the opinions expressed in the Turkish and Swiss legal systems and their case law with regard to the binding effect of the contract of inheritance. The dissertation also refers to German law to the extent where it is necessary.