Cancellaria (Cancellaria) coltrorum, new species, is described from shallow waters of the southern Brazilian Province, ranging from the Abrolhos Archipelago to Vitória. This new species co-occurs with C. petuchi Harasewych, Petit & Verhecken, 1992 but may be distinguished from it by having a broader shell with a shorter, wider spire; a proportionally larger aperture that is widest along its adapical half and has fewer, weaker lirae on the outer lip; and, most conspicuously, by having reticulate sculpture that becomes more irregular and dominated by axial ribs in latter whorls, and by being white or faintly mottled in very light tan rather than having dark brown spiral bands. The broad-ranging Cancellaria reticulata (Linnaeus, 1767) differs from both C. petuchi and C. coltrorum in having a shell with finer and more regular spiral and axial sculpture that is equal in prominence and produces a regular, reticulated pattern, as well as in having a thick, bifid posteriormost columellar fold and in lacking a thick callus that obscures the sculpture along the parietal region. Similarities in shell morphology suggest that C. mixta Landau, Petit & Silva, 2012, from the late Miocene of Panama, was a progenitor of C. coltrorum and C. petuchi, as well as the Panamic C. urceolata Hinds, 1843.