The reliance on constitutional identity by EU courts and governments has been widely discussed in legal scholarship, but less attention has been devoted to the impact of constitutional identity-based arguments on the evolution of judicial cooperation in civil matters. Member States have increasingly relied on constitutional identity in the area of private international law to claim the application of their own law or reject the recognition of foreign situations. Constitutional identity can be invoked through the public policy exception, to avoid the normal operation of private international law rules. Member States can also refer to constitutional identity when staying outside the adoption of EU private international law rules, especially regarding family law. Constitutional identity can thus impede judicial cooperation in civil matters and contribute to the fragmentation of EU private international law. Constitutional identity does not grant unfettered freedom to Member States, however. The autonomous private international law rules of the Member States must respect EU fundamental principles if the situation demonstrates some connection to EU law and the public international law obligations assumed by the Member State concerned.