Like all Uniate churches in Podlachia, it had strongly Latinized features, including an organ, pulpit, and side altars, but it uniquely retained an iconostasis.

Most Latin elements were removed from the church between 1835 and 1838 during the delatinization campaign that prepared the entire Lithuanian Uniate diocese for conversion to Orthodoxy.

During this period, the iconostasis was also replaced.The church in Mielnik is a center of local veneration of the icon of the Mother of God Oranta, dating from the late 18th to early 19th century.

It notes the existence of a church with a particularly venerated icon of the Mother of God, before which Vasylko, brother of Daniel of Galicia, prayed as he embarked on a campaign against the Yotvingians.

This was most likely a castle church, and the exact time of the establishment of the Orthodox parish in Mielnik is impossible to determine due to a lack of documents.

The sacred building was rebuilt and remained in Orthodox hands (in the Eparchia włodzimiersko-brzeska) even after the Union of Brest, to which the local faithful were opposed.

After its abolition in 1807, they were re-incorporated into the Eparchy of Volodymyr and Brest,[7] and in 1828, as part of the reorganization of the territorial division of the Uniate Church in the Russian Empire, into the Lithuanian diocese.

In May of that year, the dean of Bielsk, Kostycewicz, and the civil authority representative, Miedwiediew, inspected the church, noting the presence of several typically Uniate items and the lack of many Orthodox ones.

[17] Miedwiediew, particularly critical of the church's appearance, demanded the immediate removal of various items including a bell, confessionals, balusters, tallow lamps, and the kliros.

This led to a conflict with the local priest, Florian Zienkiewicz, who argued for retaining these elements, citing the Lithuanian bishop Joseph Semashko's precedent of not insisting on the removal of such items during church inspections.

[19] On 12 March 1838, the dean met with Miedwiediew to persuade him to allow a gradual, rather than immediate, adaptation of Uniate churches to Orthodox liturgical standards.

Miedwiediew accused the Mielnik clergy of ignoring ecclesiastical directives on delatinization and argued that all Uniate churches in Podlachia should be immediately redesigned to reflect typical Russian sacral architecture.

[19] The Lithuanian consistory discussed the situation in Mielnik in a separate session, establishing precise guidelines on retaining foreign elements in churches under exceptional circumstances.

In August of that year, he received an additional state subsidy of 448 rubles and 92 kopecks, with the condition that part of this amount be reimbursed by landowners whose peasants attended the church.

The main facade of the church is three-axis, symmetrical, with a centrally placed bell tower on a square plan, transitioning to an octagonal shape in the upper sections.

The iconostasis in the church dates back to the early 20th century and represents an Eclectic style with a predominance of Renaissance Revival elements.

[3] All the paintings were executed on wooden panels using oil technique, in a Baroque manner, characterized by dramatic poses, swirling drapery, massive proportions of the saints, painterly approach, and chiaroscuro modeling.

[25] Since the 18th century, the Mielnik parish has venerated an icon of the Mother of God, representing the rare Oranta type in Podlachia.

This icon was originally displayed for veneration in the Chapel of the Intercession of the Theotokos in Mielnik and was moved to the parish church after its extensive renovation in the early 20th century.