He represented Yugoslavia at the 1928 Summer Olympics in Amsterdam, Netherlands; he won a bronze medal with the men's all-around team, together with Stane Derganc, Dragutin Ciotti, Boris Gregorka, Anton Malej, Janez Porenta, Jože Primožič, and Leon Štukelj.

[2] In the years following, Antosiewicz participated at the 1930 World Artistic Gymnastics Championships in Luxembourg, where he won 3rd place with the Yugoslavia team and finished 15th in individual all-around.

Antosiewicz's colleague Anton Malej suffered a fatal injury at that competition after falling at the end of his routine on rings.

[3] Yugoslavia did not participate at the 1932 Summer Olympics and also missed the 1934 World Artistic Gymnastics Championships because of political tensions with Hungary.

In Trieste, his daughter met and married an American doctor and moved with him to Arkansas, United States.