What is currently (2022) accepted as the species' original description was by Osbert Salvin in 1897; he assigned it the binomial Scops sanctae-catarinae.

[6][7] Other complications arise because the several populations of genus Megascops found in southern Brazil and Argentina's Misiones Province have not been studied enough to be certain that they are correctly assigned.

The upperparts of the common morph's adult are dark brown with pale, coarse, indistinct vermiculation; its crown is somewhat lighter.

[8][7] The long-tufted screech owl is found in the southeastern Brazilian states of Paraná, Santa Catarina, and Rio Grande do Sul, in Misiones Province of northeastern Argentina, and in adjoining northern Uruguay.

Its diet includes arthropods and small vertebrates; rodents, birds, amphibians, and fish are known among the latter.

[7] The long-tufted screech owl's breeding season is not well defined but apparently includes August and September.

The male long-tufted screech owl's primary song is "a guttural, fast trill...lasting from c. 5–10 seconds and ending suddenly".

The male's secondary song is "short fast notes that become longer and more spaced, in reversed bouncing-ball rhythm".