What the international code for San Marino to call? Dial code number to open phone call in San Marino is ( 00378 ) or ( +378 ) in order to make international phone calls between San Marino and all countries of the world to unlock phone with more additional details and informations about San Marino country whereby each country is distinguished by a special telephone number, where the caller write the Republic of San Marino dial area code to opening sim card telephone line mobile or landline then the phone number.