Abstract: Endodontic treatment is performed to save periodontally intact teeth with pulpal inflammation, infection or necrosis. There are some endodontic filling materials used in dogs. The aim of this study was to evaluate the clinical application of two different root canal treatments with thermafil and gutta-percha, in dogs. Nineteen tooth roots were treated in 11 dogs. The treated teeth comprised of six first incisors, five second incisors, three third incisors and five canine teeth. Root canal treatment was decided to be performed after clinical and radiological examination. The depth of the gingival sulcus, dental mobility, haemorrhage after probing and change of tooth colour were assessed and periapical lesions and root resorption were evaluated after dental radiographic examination. In clinical examination, exposed dental pulp, dental mobility, discoloration and fracture were recorded in 14, 3, 6 and 4 teeth, respectively. Periapical lesions were recorded in 4 teeth and root resorption was determined in 2 teeth during dental radiological examination. The root canal was filled with gutta-percha in 12 tooth roots and with thermafil in 7 tooth roots. Afterwards, access openings were closed with a composite resin. Of the 12 tooth roots obturated with gutta-percha, 4 were filled with 55 mm long-gutta-percha plugs manufactured specifically for carnivores and the others were obturated with commercially available 25 mm-long gutta-percha plugs. Both techniques were observed to be applicable; however, obturation with thermafil proved to be much easier. As regards the time needed for application, thermafil was applied within shorter periods compared to gutta-percha. However, the results obtained showed that, instead of using gutta-percha cones and a file of the same size, it would be better to prefer a smaller size thermafil cone to obturate the full length of the root canal.