Self-incompatibility is considered to be a growth-limiting factor in fruit plants. In species with hermaphrodite flowers, S-locus (S-allele) has been accepted to control self-incompatibility, and the genetic control of this locus is provided by multiple genes (alleles). Pear (Pyrus communis L.) belongs to the Pomoideae from the Rosaceae family and is found to have great genetic potential in terms of ecological features in Turkey. To protect these cultivation features, national garden collections have been established across the country and Ataturk Horticultural Central Research Institute-Yalova collection is considered as genes bank. Identification of the different features of this collection (fruit quality, stress tolerance, self-incompatibility, grafting incompatibility, etc.) is of great importance for its utilization in pear breeding and cultivation. However, to our knowledge, this collection has not been characterized for self-incompatibility trait. In the current study, PCR (Polymerase Chain Reaction)-based amplification of the S-allele regions (S-1, S-6, S-7, S-8) causing the self-incompatibility in 180 pear genotypes obtained from the national pear germplasm was investigated by molecular biological methods based on the comparison of amplified products. In 180 pear genotypes, the S-6 allele was the most prevalent one with 63% frequency, while the S-8 allele was the least common allele with a rate of 4%. In allele combinations, the SI-So allele combination was the most common allele combination with a rate of 18%. and trilateral allele combinations (S-1-S-6-S-7 and S-1-S-6-S-8) were observed at a rate of 1%. Findings of the current research will enable the classification of the materials and the analysed material is likely to be used in breeding studies as well as pear cultivation.