The Monastery of Agios Nikolaos of Tsirilovo is located on the western sides of Mount Askios (Siniatsiko), 4 km SE of the modern settlement of Korissos and is 19 km from the city of Kastoria. There is no evidence of its construction, despite the opinion of the Bishop of Kastoria Filaretos (1900), who claimed that it must have been built at the end of the 18th century. Information about the monastery exists from 1872 and later, when Gregorios Diamantidis (1872-1912) was abbot and the monastery functioned as an orphanage and school for the children of the surrounding villages.
During the Macedonian War, the monastery was a refuge for the Macedonian freedom fighters against the Bulgarian aggression and imposition and hosted Pavlos Melas, as he mentions in his letters to his wife Natalia Dragoumi. On 26 February 1905, Kole’s group destroyed the monastery and then the monastery of Agios Nikolaos Koromilias, followed on 17 March by the burning of the Zigovitsis Monastery, so that on 25 March 1905, the Greek side undertook the Zagoritsani operation, which in Bulgarian literature is referred to as the ‘Zagoritsani massacre’. Since then the monastery has entered a period of decline and decay. Until 1960 it was a part of the neighbouring monastery of Agioi Anargyroi, when it was reconstructed as a women’s monastery under the guidance of Archimandrite Sevastianos Stephanopoulos. At that time the new wing and the chapel of Agios Antonios near the old complex were rebuilt, while a new katholikon, of the type of a three-aisled basilica, was erected in 1969.