He was taught the basics of drawing and painting by his father, the portrait painter, Antoni Stefanowicz.

[1] He began working primarily as an illustrator; favoring fairy tales and Orientalist themes.

Later, he painted decorations at the offices of the Land Credit Society in Lwów (now a branch of the National Bank of Ukraine) and was a co-founder of the artistic and literary magazine, Wianki (Garlands).

In February, 1915, he joined the Legion Wschodni, under the command of Władysław Belina-Prażmowski, and received the nickname "Soplica".

In 1916, he published Song of the Legionnaires: drawings of Kajetan Stefanowicz - Petty Officer 1st Regiment of the Polish Legions, a collection of engravings.