Back in Italy Brenna met Stanisław Kostka Potocki, a well-educated and rich amateur in need of professional artists. Brenna followed Potocki to Poland where he prepared two drafts of a church in Ujazdow. He received commissions to decorate Potocki's palace in Natolin, for which "compensated" himself from his patron's art collection. The two parted in a bitter conflict; "Brenna's thievery, double-dealing and desertion of his benefactor Potocki for the future czar seem the unkindest cuts of all". According to Lanceray, Brenna also painted frescoes in Warsaw for the king Stanisław August Poniatowski.