The distribution of Solanum villosum Mill., the red-berried nightshade, as a naturalised species in New Zealand is described. Observations on several distinct small populations of S. villosum over the past 20 years from the Gisborne and Christchurch/Lincoln regions of New Zealand are recorded. In addition to the distinguishing red berries, plants from both locations were shown via flow cytometry to be tetraploid. Assessment of herbarium specimens confirm that S. villosum has been observed in New Zealand for at least 70 years. Collectively, these records establish that although uncommon, S. villosum is fully naturalised and widely distributed in New Zealand. The occurrence of this species has probably been underreported due to confusion with other nightshades, especially in the absence of the characteristic yellow or red berries.