He lived an austere life as a hermit in a hut attached to the Church of St. Mark, Kraków where he served as a sacristan.

On 7 November 2018, Pope Francis authorized his equipollent beatification due to recognition of his longstanding local cultus (veneration).

[4][5] His year of birth is not known and is estimated based on his signature witnessing a donation by the Radziwiłł family to the Franciscans in Vilnius in 1439 – i.e. he had to be at least 15-years old.

[6] The Grand Duchy of Lithuania was officially converted to Catholicism only in 1387, making Giedroyć only the second generation to be baptized.

[10] He joined the Canons Regular of the Penitence of the Blessed Martyrs, an Augustinian order that had a convent in Bystryca in present-day Belarus.

[11] In 1460, together with the general superior of an Augustinian monastery and several other novices, he left for Kraków and the following year enrolled into the Jagiellonian University.

His contemporaries in Kraków included holy men John Cantius, Stanisław Kazimierczyk, Szymon of Lipnica, and Ladislas of Gielniów.

[16] He was not ordained as a priest and remained a religious brother helping clean, maintain, and decorate the church.

[27] His tomb was reopened again on 4 June 1624 and his relics were translated to a new sarcophagus suitable for public veneration on 11 August 1625.

In a window behind him, there are burning houses and people rushing away – a reference to the tradition confirmed by Miechowita that Giedroyć was a protector from fires.

These episodes include the miraculous rescue of the church of St. Mark from a fire, satanic torture that Giedroyć experienced during his prayers, and prophesying to city residents.

[31] His posthumous miracles include the message delivered by Świętosław Milczący regarding the proper burial place for Giedroyć, healing of Katarzyna Rybarka (she was a possessed woman and it was the first recorded posthumous miracle attributed to Giedroyć), saving two young boys from drowning (a son of a Hungarian merchant who drowned in the Danube and a boy in the village of Spytkowice), and reviving a stillborn child.

[33] In September 2019, a relic of Giedroyć was solemnly installed in the Church of the Assumption of the Blessed Virgin Mary, Vilnius, by Archbishop Gintaras Grušas.

[2] The sanctuary consists of three rooms: the Hall of Roots with memorabilia of the Canons Regular of the Penitence, the White Room with a Gothic and Renaissance triptych from 1520 which depicts Giedroyć with Casimir Jagiellon before the Mother of God, and a chapel dedicated to Our Lady of Giedroyć (Matka Boska Giedroyciowa).

[8][38] The 500th anniversary of Giedroyć's death in 1985 was marked with a large ceremony presided by Cardinal Józef Glemp at the St. Mary's Basilica, Kraków.

[39] Giedroyć became a Servant of God on 27 July 2001 after the Congregation for the Causes of Saints (CCS) issued the nihil obstat (no objections) decree which meant the beatification process could go ahead.

[1] On 7 November 2018, Pope Francis beatified him and authorized the CCS to promulgate the decree on his heroic virtues and on the confirmation of his cult since time immemorial (i.e. equipollent beatification which is used when the canonical process is not possible due to the lack of sufficient historical sources).