Born in Zadar, Dalmatia (then Italy, now part of Croatia), he moved to Trieste in 1948 to attend the acting school of the Piccolo Teatro di Trieste, and then to Rome to enter the Accademia nazionale d'arte drammatica. Garko began his career in the 1950s playing roles of various genres, especially in westerns and Italian-style comedies; in his later years he devoted himself to films for RAI television. He gave life to the character of Sartana (together with directors Gianfranco Parolini and later Giuliano Carnimeo), the protagonist of numerous spaghetti-westerns. In the film Il compagno don Camillo (1965) he played the character of Scamoggia, the photographer sent by the party to document the twinning.

In addition to the films he starred in, he had various television experiences. Among the many, we recall his appearance in the television series Space 1999 as astronaut Tony Cellini, in the episode entitled The Dragon's Domain (in addition to voicing Gwent in the episode The Infernal Machine in the same series), and in the television series Suspects, in the role of industrialist Martin Fisher. From 2002 to 2004 he starred in the soap opera Vivere, playing entrepreneur Pierfrancesco Moretti. He took part in a number of commercials; among others an olive oil, a wine, and finally a medicine alongside comedian Fabrizio Fontana from 1995-1997. Active now mainly as a character actor from tv