Born in Braşov, Transylvania (part of Austria-Hungary at the time), he studied in his native town and in Sibiu before completing his education in Paris. While in France, he met Dimitrie Anghel, who would became a long-time friend. In Bucharest, Iosif, Anghel and Emil Gârleanu created a literary society (1908), Societatea Scriitorilor Români ("Romanian Writers' Society"); Iosif later became associated with Sămănătorul.
His friendship with Anghel came to an abrupt end after the two writers fell in love with the same woman, Natalia Negru. She was first married to Iosif, but divorced him in order to re-marry Anghel. The latter was drawn to despair by her infidelities, and committed suicide in 1914. Iosif had died the year before, at a hospital in Bucharest, after having suffered a stroke. He was buried at Bellu cemetery.