Citizens of the European Union do not need a visa to study in Croatia. For everyone else, a student visa (Viza C) is needed.

International students who wish to study in Croatia must apply for a temporary residence permit if their stay in Croatia is for a period of more than 90 days. 

Information on countries subject to the visa requirement can be found on the website of the Croatian Ministry of Foreign and European Affairs:

The visa application along with the required documents must be submitted to the Croatian embassy or consulate in your place of residence. The application can be submitted either in person or via e-mail.

The application should be submitted well in advance of your scheduled arrival in Croatia. The usual procedure can take three months or longer (including time needed for the necessary documents to be translated into Croatian). There is also a fast-track option for handling the application and students can request this at the embassy or consulate, in which case they pay a higher fee.

The temporary residence permit is usually granted for the duration of one year or for the duration of the academic year.