The minimum qualification required to sit an EU competition and become an EU official varies whether it is an Assistant (AST1 or AST3) exam or an Administrator (AD). For Administrators, a university diploma of at least 3 years (Bachelor level) is the absolute minimum requirement, while for Assistants in the AST1 (entry level), no diploma is required other than a high school or vocational school certificate (though for AST1 who have no specialised education, generally 3 years of work experience is needed).
For AST3 level, a university diploma is not required if the candidate possesses a high school level education and 6 years of relevant work experience, otherwise a diploma is needed (usually in field that is relevant to the topic of the competition, e.g. project management or audit) with only 3 years of work experience. The diploma must be recognized by an EU member state's public authority.
See also:
Admission Criteria, EU Officials