In this study, animals from the Kivircik breed of sheep and two closely related breeds (Pirlak and Karacabey Merino) were analysed by using 15 microsatellite markers to evaluate the genetic diversity within the Kivircik breed and to elucidate its relationship with the other two breeds. A total of 244 alleles were detected on all of the 15 microsatellite loci studied. While the Kivircik population of sheep showed a significant deviation from the Hardy-Weinberg equilibrium (HWE) for all 15 loci, both the Pirlak and Karacabey Merino breeds showed a significant deviation from the HWE for 10 loci. The mean observed heterozygosity and F-IS exhibited ranges of 0.63 to 0.72 and 0.0672 to 0.2139, respectively. The highest mean number of alleles value and the greatest number of private alleles were observed in the Kivircik population. While microsatellite analysis revealed high genetic diversity in breeds investigated, a high level of inbreeding was also observed between different Kivircik populations and other two breeds. The genetic differentiation between breeds was found to be low. The Kivircik from Istanbul and Bursa were the most closely related genetically, while the Kivircik from Manisa differed from the other populations. In addition, the Karacabey Merino and Pirlak breeds grouped together.