Pelargonium denticulatum belongs in the family Geraniaceae, a large cosmopolitan family of approximately 11 genera and 800 species in subtropical and temperate regions of the world. The South African genera in the Geraniaceae family are Monsonia, Sarcocaulon, Pelargonium, Erodium and Geranium. There are approximately 270 species of Pelargonium which occur in S, E and NE Africa, Asia, St Helena, Tristan da Cunha, Madagascar, Australia and New Zealand, most of which (± 219 species) occur in southern Africa, with a large concentration of more than 135 species in the southern portion of South Africa between Nieuwoudtville in the west and Port Elizabeth in the east. Pelargoniums are often incorrectly called geraniums.

The genus Pelargonium gets its name from the resemblance of the shape of the fruit to the beak of a stork, pelargos in Greek, while the Latin species name, denticulatum, refers to the finely toothed leaf margin. This species has the common name of tooth-leaved pelargonium. In 1789 the species was introduced into England from the Cape by Francis Masson, a Scottish botanist who was sent by the Royal Botanic Gardens, Kew to collect live plant specimens.

Robert Sweet, an English botanist and horticulturist, published a description and colour illustration in Geraniaceae 2: t. 109 (1822). He mentions that the species was grown in Kew until 1821 but there was no evidence to suggest that Nicolas Jacquin, a Dutch and Austrian botanist, obtained the material, which he used to describe the species in 1797, from Kew. In Vienna the Museum of Natural History has several specimens of Pelargonium denticulatum. These specimens do not have any inscriptions in Jacquin's handwriting. There is also no indication that he used any of these specimens for his original descriptions.