What the international code for Slovakia Slovak Republic to call? Dial code number to open phone call in Slovakia Slovak Republic is ( 00421 ) or ( +421 ) in order to make international phone calls between Slovakia Slovak Republic and all countries of the world to unlock phone with more additional details and informations about Slovakia Slovak Republic country whereby each country is distinguished by a special telephone number, where the caller write the Slovakia Slovak Republic dial area code to opening sim card telephone line mobile or landline then the phone number.