Born into a Jewish-Polish family[1] in Wołkowysk, Russian Empire (now Belarus), he settled in Paris around 1890 and began his professional chess career in 1894.

He had minus scores, however, against newer players such as Siegbert Tarrasch (+5−9=3), Frank Marshall (+28−34=18), Akiba Rubinstein (+3−5), Géza Maróczy (+5−10=5) and Carl Schlechter (+13−20=13).

He won at Atlantic City 1921 (the eighth American Chess Congress) and took third place at Lake Hopatcong 1923 (the ninth ACC).

In Marshall's Best Games of Chess he wrote that Janowski "could follow the wrong path with greater determination than any man I ever met!"

He also noted that Janowski was sometimes unpopular with his colleagues because of his predilection for doggedly playing on even in an obviously lost position, hoping his opponent might blunder.