The aim of this paper is to establish the way the rules of European Law influence legal standardisation of administrative procedure in the Republic of Croatia. The sources of European Law adopted from the Council of Europe and the European Union are analysed as two international organisations which have to some extent significantly impacted on the development of Croatian law. Particular attention is paid to comparing Croatian legal rules which are applied in conducting proceedings. These are related to lawfulness, equal treatment, impartiality, equity, access to the case’s file, the party’s pleading, explanation of the administrative decision, proportionality in decision making, resolution within a reasonable timeframe and European legal standards of regulation and carrying out administrative proceedings. In conclusion, the author assesses the overall harmonisation of Croatian administrative procedural law with European standards.