In section Leiopetali, the diploid chromosome numbers were reported from only six of total 25 taxa. There is no karyological data relating to other 19 taxa. In this study, it is intended to determine the diploid chromosome numbers of taxa of section Leiopetali. The diploid number of 13 species were detected, four of which were recorded for the first time and nine numbers compatible with the previous reports. Twelve species were diploid with 2n = 2x =30. D. leptopetalus was diploid and polyploid, which reveals only one polyploidy level of tetraploidy (2n = 4x = 60). Polyploidy might have played a role in the karyotype evolution of the genus. One of the most important reasons for this situation is that although polyploidy is observed in the genus Dianthus, the dysploidy mechanism that causes a change in the basic chromosome number has not been found until now. The basic number is x = 15 according to the all chromosomal reports. In conclusion, this study reports new data into the karyological characteristics of section Leiopetali (genus Dianthus) that can be useful for interpreting or understanding relationships among sections.