Abstract: It seems to be undisputed today that the harmonization of private law in Europe cannot take place without taking fundamental rights into account. Yet many questions still exist as to how and to what extent EU and national private law can and should be influenced by fundamental rights enshrined in the EU Charter of Fundamental Rights. This contribution aims to explore gateways to the EU constitutionalization of private law, constraints thereon, and challenges posed thereby, with a particular focus on contract law in the consumer, employment, and financial services context. After a methodological introduction explaining the special nature of the fundamental rights protection in the EU legal order (s. 1), the authors develop a general framework within which the EU constitutionalization of private law takes place (s. 2). Subsequently, they proceed to examine the fundamental rights scrutiny of EU law and national laws within the scope of EU law (s. 3), the interpretation and application of EU law and national law within its scope in conformity with fundamental rights (s. 4), as well as the controversial concepts of the positive obligations to protect fundamental rights in private relationships (s. 5) and the direct horizontal effect of fundamental rights (s. 6). The contribution concludes with some final observations (s. 7).