The exact construction period is not known. The primitive Romanesque church consisted of a single nave hall, ended by two apses (no longer existing); both had an altar: one dedicated to St. George, the other to St. Sisinius (originally from Cappadocia, he was sent by St. Ambrose, together with Martirio and Alexander to evangelize the Val di Non where they were killed by pagans). It has undergone changes and reconstructions over the centuries which have altered its original appearance.

It served as a parish church until 1574, the year of the visit of St. Charles Borromeo who decided to transfer the parish benefit to the other religious building in Crevenna, larger in size and located in a more central place: Santa Maria Maddalena.

The oratory is located outside the town of Crevenna. Beginning in 1810, the cemetery was built around it.

In 1975, following restoration work, the external walls were restored to their original appearance, with exposed stones, as the plaster that covered them was removed. The facade has a portal decorated at the top with a scroll motif and flanked by two small windows; the upper part of the forehead is characterized by a lunette and a tympanum.

Along the left side of the building, only a few traces remain of the foundations of the Romanesque bell tower with loopholes, single and mullioned windows, demolished at the beginning of the nineteenth century.

The interior of the church, with a single nave and the presbytery from which the sacristy is accessed on the left, is poor in decorations.

On the cross vault of the presbytery area there is a frescoed panel, probably from the eighteenth century, depicting an angel supporting a crown accompanied by two winged cherubs.

A fresco, datable to the end of the fourteenth century, representing the Madonna enthroned with Child, has been reused as an altarpiece: the face of the Virgin was retouched in the mid-eighteenth century by the Lugano brothers Giuseppe Antonio and Giovanni Antonio Torricelli, active artists in Caslino d’Erba in the decoration of the chapels of the Via Crucis that surround San Gregorio.