When his wife and daughters died at very young ages, Radonja resigned his feudal position and after Autumn 1364 took monastic vows and name Gerasim while his father
Branko Mladenović was still alive. There he served and helped with great merit Hilendar and also the monasteries of
Koutloumousiou and
Agiou Pavlou monastery. Thanks to the Radonja's influence, Vuk Branković became the first of Serbian feudal lords who gained
ktitor's privileges in Hilandar after the
fall of the Serbian Empire, beginning in 1371. The earliest mention of Radonja under his monastic name Gerasim was in a charter of Vuk Branković issued to
Hilandar Monastery in 1376/77. Around 1380 Radonja, together with
Arsenije Bagaš, bought ruined
Agiou Pavlou monastery from
Xeropotamou Monastery and reconstructed it. In period 1379—89 Radonja was a priest in the Hilandar Monastery and was again mentioned as Gerasim, a brother of Vuk Branković, in the 1389 document written by
Prince Lazar. Around 1392 Radonja and group of notable "elders" from Hilandar visited court of the
Lazarević family, successors of
Prince Lazar, and requested a church in Ibar and its estates to be granted to Hilandar, according to the promise given by its former lord, Obrad Dragoslavić. After the death of Vuk Branković in 1396, Radonja took Vuk's body to the Agiou Pavlou monastery on
Mount Athos. Radonja died on 3 December 1399 probably in Agiou Pavlou monastery. == Gerasim's Chronicle ==