ABSTRACT. – The aim of this study was to investigate the genetic variability and origin of the nonindigenous marine mollusc population of limpet snail, Siphonaria pectinata Linnaeus, 1758, recently identified in the Adriatic Sea in Split (Croatia) by using molecular data. Four molecular markers were PCR amplified and sequenced: two mitochondrial (16S rDNA and cytochrome oxidase I, COI) and two nuclear ones (ITS1 and 18S rDNA). Our results showed that the introduced S. pectinata population exhibited substantial genetic variation because among twelve analyzed individuals we identified three 16S rDNA and four COI haplotypes as well as four different ITS sequences. This result suggests that the founder population was composed of several distinct haplotypes. In order to identify the geographic origin of the population that colonized Croatia, we performed phylogenetic analyses of 16S rDNA and COI haplotypes of the Croatian and overall S. pectinata populations retrieved from GenBank. COI and 16S rRNA haplotypes are shared among native Spanish and non-native Croatian populations which suggests that the analyzed Croatian population originates from a stock similar to the Spanish one. This is the first population study of this invasive mollusc outside of its native range of distribution and the obtained results might serve as a starting point for its future monitoring