Document authentication through diplomatic channels

In order to authenticate documents through diplomatic channels, you must submit them as follows:

Degrees and academic certificates to the Ministry of Education of the home country, and birth and nationality certificates to the appropriate national ministry.
The Ministry of Foreign Affairs of the country where the documents were issued.
The Spanish consulate or diplomatic representative in that country.
The Authentication Division of the Spanish Ministry of Foreign Affairs, C/ José Abascal 41, Madrid.

Authentication is not necessary for the countries of issue having signed the Hague Convention. In such cases, the only requirement is that the relevant authorities of that country attach the Hague Apostille to the documents.

The documents issued by the consulates or diplomatic representatives of foreign countries in Spain must also be authenticated by the Spanish Ministry of Foreign Affairs.

Translation into Spanish

All documents issued in a foreign language must be submitted together with their Spanish translation, which can be done through:

Any Spanish consulate or diplomatic representative abroad.
The consulate or diplomatic representative in Spain of the applicant's home country or, when appropriate, of the country issuing the document.
An official translator.

Further information

http://www.mecd.gob.es/educacion-mecd/areas-educacion/sistema-educativo/convalidaciones/titulos-no-universitarios.html