Chromosome morphology of Nepeta viscida Boiss. (Lamiaceae) naturally in Turkey was analyzed in detail. Squash preparation method was used for chromosome study in this species. The somatic chromosome number was counted as 2n=18 in Nepeta viscida. The basic chromosome number of the genus was x=9. The shortest chromosome length is 1.03 μm, the longest is 1.68 μm, and haploid chromosome length is 12.41 μm. Chromosome arm ratios are measured as 1.07–1.71. Centromeric index varies between 3.71 and 5.14, and relative lengths vary from 8.34 to 13.54. The karyotype was determined using Image Analysis System (Bs200Pro). The karyotype formula of this species consists of eigth median chromosome pairs and one submedian chromosome pairs. The ideogram was drawn based on centromeric index and arranged in the decreasing size order. The karyotype was determined for the first time in this study, respectively