Lankascincus fallax is an endemic, but widespread species of skink distributed throughout Sri Lanka, including all bioclimatic zones (elevations from 0 to 1,200 m a.s.l.). After thoroughly comparing morphology and morphometry between populations in different bioclimatic zones, we recognize it as a single morphospecies. We revise the systematics of Lankascincus fallax based on molecular and morphological data providing a comprehensive re-description of the adult syntype collected from either Ratnapura or Trinkomalee (sic), Sri Lanka. We provide the first-ever constructed phylogeny of Lankascincus representing five species (out of nine) based on GenBank data. In addition, we examined all the type specimens of the two synonymized species, Sphenomorphus rufogulus and Lankascincus deraniyagalae. We also provide a comprehensive discussion on the distribution of L. fallax.