The treasury of the parish church of the Immaculate Conception of the Blessed Virgin Mary in Kaštel Štafilić is the repository of a cult object of great importance to the faithful, namely the icon of the Virgin Mary and Child, which is protected and considered a miraculous object.

The history of this icon is closely linked to the figure of Ivan Štafilić (1473-1528), a Croatian bishop who came from a craftsman family. Ivan's father, Stjepan Štafilić, acquired a fortune that allowed him to build the castle of Kasztel. While serving as a papal legate, Ivan Štafilić served at Wawel Castle in Krakow, where he established historically significant Polish-Croatian relations. This is exemplified by Sigismund I the Old (1467-1548) granting him Polish nobility with his coat of arms in 1512, traced by the eagle appearing in the family coat of arms.

According to tradition, before leaving Krakow, Ivan Štafilić was given an image of the Virgin and Child as a gift. It was this painting that, according to legend, was supposed to protect Kaštel from Turkish invasion.

Analysing the artistic aspects of the icon, it can be seen that its gilding and the way the figures are depicted suggest its creation in the late medieval period, estimated to be between the 13th and 15th centuries. In the icon, the faces of the Virgin and Child have been painted in a manner characteristic of the Byzantine tradition. Their faces display idealised features, with long, delicately defined noses, eyelids and narrow lips, giving them an expressive yet subtle character. Mary's face exudes serenity and majesty. The eyes are large and wide open to symbolise her all-seeing nature and spiritual perception. The mouth is closed and appears thin, which may suggest her inner contemplation. Her complexion is dark and unnaturally smooth, reinforcing the impression of holiness. The infant Jesus is depicted with the characteristics of a 'little adult' - with a proportionally small head and expressive facial features, which is meant to emphasise His divinity and omniscience, as well as wisdom beyond childhood. His gaze is directed towards the viewer, which may be an invitation to spiritual connection. The infant's skin colour is similar to that of Mary. Both faces are modelled with chiaroscuro, although in a more schematic manner than in Western Renaissance art, which is typical of Eastern iconography. The background behind the figures is gilded, which not only introduces an element of opulence and splendour, but is also intended to symbolise the heavenly, divine dimension of the figures depicted. The contours are clear and the facial details - eyes, mouth, eyebrows - are marked with dark lines, giving depth and clarity to the composition. The traditional Byzantine tones of red and gold are a testament to iconographic conservativeness, the icon retains the characteristics of the Eleous type, presenting Mary in a tender gesture embracing Jesus, who in turn touches Mary's cheek with his cheek. This type of representation strongly affects the faithful by emphasising the human dimension of Christ's incarnation and His future suffering and death for the sake of humanity. It is therefore not only an expression of affection between mother and son, but also a theological symbol of salvation and mercy. Unlike most of the depictions on the Croatian icon, the child does not embrace his mother's hand, but raises his fingers in a gesture of blessing. This detail may be taken from the popular Hodegetria icon type, in which Mary points to Christ as the path to salvation, providing a unique synthesis of both iconographic traditions.

In October 2012, the Polish community, together with local authorities and cultural institutions, commemorated the 500th anniversary of the awarding of the title of nobility to Ivan Štafilić by placing a commemorative plaque in the church.