Adult male SVL ranges between 33 to 49 mm, with SVL in adult females measuring 32 to 50 mm. The head is longer than broad with a subovoid to elliptical snout in dorsal view. The eyes and tympanum are large. Finger I is longer than finger II. Subarticular tubercles are round and projecting. Supernumerary tubercles are lacking on both hands and feet. Tarsi and soles are smooth. Leptodactylus poecilochilus has one to three pairs of dorsolateral folds, but otherwise the dorsum and venter are smooth. Soles and tarsi are smooth as well. The inner metatarsal tubercle is small and elongated; the outer metatarsal tubercle is present but tiny. A smooth, low inner metatarsal fold is present. Neither nuptial pads nor spines are present in males. Adult males have vocal slits that are paired and elongated, as well as paired external lateral vocal sacs (Savage 2002).
Coloration of the dorsum is brownish gray with a spotted or striped pattern. The dorsolateral folds may be the same brownish gray color, but can also have cream or dark brown pigmentation. There is a middorsal light stripe often present. Dark canthal stripe. Dark supratympanic fold. Upper lip has dark spots or bands. Chin usually unpatterned but sometimes has a dark border. Hind limbs are barred dorsally. Across the posterior thigh surface there is a distinctive longitudinal white stripe. Venter is white. Iris is gold. Vocal sacs are black (Savage 2002).
Tadpoles are medium-sized, measuring 36 mm in total length at stage 40. Mouth anteroventral, directed ventrally. Body ovoid. Eyes and nares are dorsal. Spiracle is lateral and sinistral. Vent tube is medial. Caudal fin pointed. Oral disc is small and complete. Beaks and 2/3 denticle rows are present. Above the mouth there is a broad gap in A2. Absent above the mouth, labial papillae are present mostly in two rows. Body is blotched, with darker dorsal color and lighter ventral color. Tail is spotted and blotched (Savage 2002).
A Spanish-language species account can be found at the website of Instituto Nacional de Biodiversidad (INBio).