A new Neotropical temnocephalan species is described from Aegla jarai Bond-Buckup & Buckup, 1994 from Santa Catarina, Brazil and recorded on Samastacus spinifrons (Philippi, 1882) from five locations (Región de Biobío, Región de la Araucanía, and Región de Los Lagos) in Chile. Temnocephala catarinensis sp. nov. differs from 10 other species of Temnocephala Blanchard, 1849 epibionts on Aeglidae Dana, 1852 and/or Parastacidae Huxley, 1879 by having the following combination of characters: 1. a long and slightly curved cirrus; 2. an introvert with two distinct portions, a proximal one with grooves and no spines and a distal one with small spines with a strong base; 3. a single vaginal sphincter, well-developed and slightly asymmetrical; 4. a very short vagina with a weak muscular wall; 5. an almost triangular epidermal 'excretory' syncytial plates, with external margin in half circumference, sometimes reaching laterally the margin of body. The specimens of S. spinifrons have slightly larger measurements than specimens of A. jarai. The cirrus total length and introvert length, despite being larger, have almost the same number of spines in the distal portion. The shape of the EPs is similar in specimens from both hosts. The new species share some similarities with Temnocephala axenos Monticelli, 1898, Temnocephala mexicana Vayssière, 1898, Temnocephala kingsleyae Damborenea, 1994, and Temnocephala mertoni Volonterio, 2007, but the characters that differentiate them are presented and discussed. The new species has a wide geographic distribution represented by a large distance between the sampled locations (2,637 km) and separated by the Andes. This is not the only species with very distant records from each other as Temnocephala iheringi Haswell, 1893 and T. axenos or separated by the Andes as Temnocephala chilensis (Moquin-Tandon, 1846) and Temnocephala monticellii Ponce de León, Rudolph and Volonterio, 2020.