Onnig Avedissian was born in Brusa (nowadays Bursa) on November 21, 1898. At the age of two, he moved to Constantinople with his family, where he acquired his primary and secondary education (1904–1915). During the summers of 1920-1921, he was tutored by painter Serovpé Kurkjian (1872-1924), who enhanced his inclination for art.

With the support of his parents, Avedissian decided to study art in Europe. In 1921 he was enrolled as a student in the School of Graphic Arts of Vienna, where he studied until his graduation as an expert in etching in 1925. He married in 1922 and had a son. He participated in the annual salon of the Viennese Association of Artists in 1923 for the first time. He studied painting at the Academy of Fine Arts in Rome (1925-1927).