This frog has a gray-brown to tan dorsum, a white ventrum, and a deep purple groin. There is a poorly distinguished black mask around its eyes. (Guyer and Donnelly 2005). Smilisca sordida has weak crossbands on its back legs, as well as dark spots on the head and back (Leenders 2001). The posterior of the thigh is deep purple with small blue, green or tan flecks. Breeding males have a white vocal sac (Duellman 2001). This species has a yellowish brown iris with black net-like veins (Guyer and Donnelly 2005).
The larval body is moderately sized and reaches approximately 32 mm in length. The caudal musculature is beige with light red specks which vary from dark to light areas along the midline. The body is ovoid, the mouth ventral, and the nostrils and eyes are dorsolateral. The large, entire oral disc has well developed beaks with two-thirds denticle rows. The beaks are bluntly serrate and the papillae are in two rows which are sideways and ventral to the mouth. There are numerous extra rows at the corner of the mouth, but none higher than the mouth. The spiracle is lateral and sinistral. The vent tube is dextral. The tail is moderate in length and pointed, with moderately-sized caudal fins (Savage 2002).
The tadpole body is beige and the belly is pale beige with a silver or white tint. The iris is bronze (Savage 2002).
Smilisca sordida is easily confused with two other Smilisca species (Guyer and Donnelly 2005). It is distinguished from Smilisca phaeota by the absence of a white stripe on its upper lip, and it does not have the spot beneath its eye that is characteristic of Smilisca baudinii (Leenders 2001) . Duellman states that specimens taken from Honduras and Nicaragua are like those from the Meseta Central in Costa Rica, having bluish white mottling on the posterior flank and lacking light specks on the posterior surfaces of the thighs. These specimens are smaller and modestly different from those in the Pacific versant in Costa Rica, and indicate that the latter may represent a species different from Smilisca sordida (Duellman 2001).
A Spanish-language species account can be found at the website of Instituto Nacional de Biodiversidad (INBio).