The first evidence of the existence of a church in Ornica dates back to the 14th century, when a small chapel dedicated to Sant'Ambrogio was erected on the site of the present building, governed by a chaplain. The church was subject to the parish church of Santa Brigida, from which it detached in 1456, becoming an autonomous parish guaranteed by an income to support the parish priest, paid for by the population.
The Acts of the pastoral visit of St Charles on 23 October 1566 give us some information about this church: it had five altars, the high altar of which was consecrated and decorated with a beautiful altarpiece (probably the polyptych of St Ambrose), it also had a tiny sacristy and a bell tower with two bells.
Of this church, which was very small, all that remains today is the presbytery, which corresponds to the current sacristy, with a cross vault frescoed by Angelo Baschenis.
The current building, in late Baroque style, with a Latin-cross nave divided into three bays and a low arch vault, was built in the first half of the 18th century, on the initiative of the parish priest, Don Giacomo Pesenti, who invested a large part of his private assets in it.
The pride of the church in Ornica is the polyptych of Sant'Ambrogio, a 16th-century work attributed to a painter of the school of Cima da Conegliano. The polyptych is enclosed in its original frame, finely carved and gilded, divided into four registers and includes fourteen panels.