Trade secrets have become one of the most valuable assets of the modern, knowledge-based economy, yet for a long time they enjoyed markedly uneven protection across the Member States of the European Union. Directive (EU) 2016/943 was adopted to remedy this fragmentation by establishing, for the first time, a common definition of a trade secret together with a harmonized set of civil measures, procedures and remedies against the unlawful acquisition, use and disclosure of such information. This thesis critically examines the degree of harmonization actually achieved under the Directive, the effectiveness of its enforcement mechanisms, and the practical consequences for businesses operating across several jurisdictions. Adopting a doctrinal and comparative method, it analyzes the substantive framework of the Directive, its transposition in selected Member States, in particular Germany, France and Italy, and the emerging case law of the Court of Justice of the European Union. It further situates the European regime within the international legal framework shaped by Article 39 of the TRIPS Agreement and compares it with the United States Defend Trade Secrets Act of 2016. The study argues that, although the Directive establishes a solid common foundation, its character as an instrument of minimum harmonization, combined with divergent national procedural traditions and the unresolved private-international-law treatment of trade secrets, leaves significant gaps in legal certainty for cross-border business. On the eve of the European Commission’s first comprehensive evaluation of the Directive, the thesis proposes a series of targeted measures to strengthen harmonization, enforcement and legal predictability.