Rapid diagnosis of dermatophytosis is essential for early treatment induction and prevention of spreading to other animals and humans. No single diagnostic test is identified as the “gold standard”. The purpose of the study was to evaluate the sensitivity of adhesive tape impression (ATI) cytology in dermatophyte identification and to compare three diagnostic tests for dermatophytosis. Thirty dogs, with alopecia (n = 19) or kerion (n = 11), and fifteen cats with alopecia were included in the study. Dermatophytosis was diagnosed with tape preparations in 82.2% (37/45) of cases, while with hair plucks in 66.7% (30/45) and fungal culture in 80% (36/45). In kerions, tape preparations and fungal culture had the same sensitivity (10/11, 90.9%) that was higher than that of hair plucks (4/11, 36.4%). The sensitivity was higher in cats than in dogs with alopecia for all tests, 80% versus (vs.) 73.7%, 86.7% vs. 68.4%, and 93.3% vs. 68.4% for cats and dogs for hair plucks, fungal culture, and tape preparations, respectively. No significant difference was found between the three tests, except for dogs with kerion. Hair plucks were less sensitive than fungal culture in kerions (p = 0.041), while in comparison with tape preparations they were marginally not significantly different (p = 0.078). ATI cytology is a useful diagnostic test in dermatophytosis, in dogs with kerion as well as cats.