A portrait of Grand Duke Vytautas of Lithuania, painted in Lithuania in the 17th or 18th century, hangs at the end of the left aisle near the sacristy. Vytautas is represented with the crown of a grand duke, wearing a mantle over his armour. Until 1854, the painting used to hang in the Church of Our Lady Comfort of the Afflicted, used by the Augustinian friars, whose monastery was endowed by Grand Duke Vytautas. The image was painted for the Augustinian church in Brest Litovsk, which was also endowed by Vytautas.

Beneath the portrait is set a black marble plaque framed with sandstone. The first monument to Vytautas was erected in 1573 by Bona Sforza, but it was destroyed in the fire of 1610. The current plaque was created in 1853 on the initiative of Eustachy Tyszkiewicz. The author of the memorial is sculptor Józef Kozłowski.