It is a richly decorated, five-tier high main altar, dating from 1643. It represents the late Renaissance style. It fills the entire surface of the eastern wall of the presbytery, contains numerous paintings and figural sculptures, and is covered with polychrome relief decoration with auricular style motifs.
The main painting comes from 1643 and was painted on canvas by the Gdańsk artist August Ranisch. It depicts the patron saint of the church, St. Nicholas kneeling before Christ, who hands him a book, and the Virgin Mary placing a mitre on his head. The painting occupies the height of the second and third tiers of the altar.
On the fourth tier, there are two oval paintings of St. Dominic and St. Francis. On all the tiers there are numerous figures of saints, e.g., St. Stanislaus with the Piotr at his feet, St. Adalbert with an oar, St. Jacek Odrowąż (Hyacinth) with a figure of the Madonna in his left hand, St. Casimir, Blessed Ceslaus Odrowąż.
The altar composition is crowned with the figure of the Madonna in a radial mandorla.