The interior, richly decorated with marble, is undoubtedly one of the most interesting and artistically coherent designs. Its distinguishing feature is the richness of colors, unparalleled in other Polish Chicago churches. Some elements consist of several shades and kinds of marble complemented with alabaster. They are counterpointed by the more modest design of the altars, whose forms, inspired by Romanesque Revival art, correspond perfectly with the austerity of the main body of
the church. The whole is complemented with elaborate bronze gratings and details.