Santin was born in Rovigno (Rovinj), Austria-Hungary (modern day Croatia), on 9 December 1895,[2] and was ordained on 1 May 1918.

Economic difficulties didn't allow him to pursue priesthood; however, thanks to the help of a priest in Capodistria he was able to go to high school and entered the seminary, from which he graduated in 1915.

[3] The Italian episcopate "was convinced that it was possible to use fascism for the purpose of 'Catholic restoration' after more than half a century of anticlerical liberal governments.

"[3] He demanded complete Latinization of the liturgy, thus abolishing the šćaveta (from italian schivaetto; church books from Croatian coastal areas written in the vernacular Chakavian language, dating back to the 15th century, containing epistles and gospels that are read at Mass throughout the year[6][7]),[4] which he considered an abuse.

"[8] Santin later stated that he "attempted to make both the [local] clergy and the people understand that we couldn't go on with the quarrels that had upset the spirit and the peace of the sacre funzioni, and that adapting liturgically to Latin was obeying to the Church.

"[8] After the war, Santin was accused both in Yugoslavia and Italy of having been too close to Mussolini's government, and because of that he may be held partially responsible for the process of italianization in the Julian march.

[8] Santin advocated that the Julian March remain part of Italy, and later opposed the passage of northern Istria to Yugoslavia.

He opposed the Catholics' opening to the liberal left-wing, which, nonetheless, came about, and produced the election of Slovenian Dušan Hreščak to the municipal council in 1964.