I describe the tadpole of Colostethus kingsburyi (Boulenger, 1918), a dendrobatid frog that occurs in Ecuadorian Amazonia at the foothills of the Andes. The tadpole of C. kingsburyi is similar to other dendrobatid tadpoles with respect to body shape, labial tooth row formula, arrangement of papillae of the oral disc, jaw serrations, and location of the spiracle and vent tube. It differs in the number of papillae on the oral disc and by having the terminus of the tail heavily blotched. The number of marginal papillae around the oral disc in tadpoles of C. kingsburyi varies ontogenically; this type of ontogenetic variation has been documented only in a few Colostethus tadpoles and may be more widespread than previously recognized. Phenetic resemblance of C. kingsburyi and tadpoles of Allobates femoralis is remarkable and supports a current hypothesis of a close phylogenetic relationship between these taxa. The identification of larval synapomorphies requires analysis of a larger dataset.