The Concert of Europe and its congress diplomacy had both positive and negative outcomes by the end of the 19th century:

• The congress system proved to be the best mechanism for mediation and arbitration among European powers. Besides, meeting periodically at the congresses contributed to the construction of a collective identity among Europeans, because the common diplomatic language and codes created shared understandings among states. However, the system was confined to Europe. NonEuropeans were neither familiar with the congress diplomacy nor shared a common understanding of diplomacy and customs.

• The Concert contributed to the cooperation among European states for maintaining peace as well as the governance of the system. However, it did not produce permanent international bodies for resolving the disputes. Nor did it contribute to the institutionalization of international regulations and norms by way of codifying them into international law. The Concert never encouraged its members to create further organizations. As such, it was only an instrument of collective diplomacy, not an organizational body to regulate the international system. Its structure was determined by the great powers which produced rival blocks by the end of the century.

• In European politics the congress system served as a tool of peacebuilding after the armed conflicts. However, it failed to prevent the confrontations of Europeans with non-European powers as the cases of US-Spanish War of 1898 and the Russo-Japanese War of 1905 illustrated.

• Although the congress system was the primary tool of great power diplomacy, the outcome of the congresses never surpassed the will and interests of their organizers. In other words, the Concert was designed to favor the great powers and contribute to their common interests. Probably, this is the most negative legacy of the Concert for future international organizations, because it undermined the principle of sovereign equality.