The song of Colima Pygmy-Owl is described as "hollow hooting ... with [a] variable, often increasing, number of notes, hoo-hoo, hoo-hoo-hoo, hoo-hoo-hoo-hoo, hoo-hoo-hoo-hoo-hoo ... etc., [with] up to 24 notes (or more?) in [a] series" (Howell and Webb 1995). The first inter-note interval is longer than the second, after which the pacing is fairly steady (Howell and Robbins 1995). The song has a "hollow, wooden to slightly plaintive quality that suggests the Ferruginous Pygmy-Owl (G. brasilianum)" (Howell and Robbins 1995).
For a representative audio recording with sonogram, see audio
Other vocalizations of Colima Pygmy-Owl include "quavering rolls which may precede [the] hooting series" (Howell and Webb 1995).