Hyalinobatrachium fleischmanni is a relatively small frog with males ranging from 19.2 to 25.5 mm (Wild, 2003) and females reaching 23 to 32 mm (Guyer, 2005; Savage, 2002). This frog has a relatively flattened body, broad head, round snout, and forward-directed eyes. It has pale green skin with yellow or yellowish green spots and a white, partly transparent belly showing tiny white bones (Wild, 2003). The heart and anterior half of the liver are obscured by a white sheet of guanine. This layer of guanine also wraps around its digestive system (Guyer, 2005). Fingertips are yellow (Wild, 2003). The eye has a gold-colored iris surrounding a horizontally elliptical pupil (Leenders, 2001). Hyalinobatrachium fleischmanni is very similar in size and color to the Yellow-flecked Glassfrog (Cochranella albomaculata) and the Powdered Glassfrog (Hyalinobatrachium pulveratum). However, the latter two species have exposed digestive organs which are not wrapped in a white guanine sheath (Guyer, 2005).
 

A Spanish-language species account can be found at the website of Instituto Nacional de Biodiversidad (INBio).