[2][3] He was a teacher before reinvigorating clandestine religious orders that the Russian Empire had suppressed during their occupation of Poland.

[2][3] His beatification, by Pope John Paul II, took place on 16 October 1988 in Saint Peter's Square, Rome.

Even in the hostile climate created by the Russian occupants against the Latin Church Koźmiński carried out his apostolate in secret.

The Congregation for the Causes of Saints validated the informative process on 1 February 1985 before receiving the Positio dossier from the postulation in 1986; that September theologians approved.

One month later on 16 March he was named as Venerable after Pope John Paul II confirmed his heroic virtue.

validated this process twice on 1 February 1985 and on 30 April 1987 before a medical board approved the miraculous nature of the healing on 14 October 1987.

John Paul II confirmed this miracle on 1 September and beatified Koźmínski on 16 October in Saint Peter's Square.