Sardine (Sardina pilchardus) is one of the most important species among Turkish fisheries and is broadly distributed along its coastal waters. In the present study, mitochondrial DNA sequences from the cytochrome b (cytb) gene were examined to assess the genetic diversity of sardines inhabiting Turkish coastal waters. A fragment of sardine cytb DNA from each sample collected from 8 representative regions along the coastal zones was amplified by PCR analysis and subsequently sequenced. The results of sequence analysis determined the existence of variations in 16 single nucleotide sites within the 452 bp fragment of the cytb gene examined in the present study. Phylogenetic trees and pairwise analyses demonstrated a very small divergence (0.002%-0.44%) between the populations, suggesting the lack of population subdivisions. Furthermore, the results of this study revealed a pattern of high nucleotide homology among the adjacent populations, and a small number of nucleotide changes among disjunct populations, leading us to conclude that there is a genetic admixture among the populations inhabiting the coastal waters of Turkey, especially in those geographically close to each other. The results of this study suggest that sardine populations of coastal Turkey are part of a larger, self-recruiting population whose boundaries extend beyond the investigated area.