Senecio reitzianus was described from sand dunes in Lagoa da Conceição (Florianópolis, Santa Catarina state, southern Brazil). The species remained to be known only from the type. Almost seventy years later, we discovered a population of this species in Costão do Santinho, about 20 km from the type locality. A detailed account of this population is provided and its conservation status is assessed. We also present photographs of this species from the wild and also of the holotype, as well as a new description and comparisons with similar species in the genus. Our results reinforce the urgent need of further field work, especially on data-deficient species, in order to have a chance to prevent the species extinction.