The aim of this study was to determine the blood cells parameters of Anatolian and Thracian Bombina bombina populations. The size and counts of various blood cells were analyzed in 29 mature Bombina bombina specimens belonging to two populations (Durusu-Istanbul and Döşeme Bataklığı–Adapazarı) in northwest Anatolia. The mean erythrocyte count was determined as 251.429/mm3, that of leucocytes was 2.114/mm3, and that of thrombocytes was 12.857/mm3. There was no significant sexual variation in blood cell counts of our B. bombina sample which was collected during their breeding season. The leucocyte differential counts and staining properties of blood cells were also determined. Interspecific comparisons indicate that northwest Anatolian B. bombina samples share general features with other anurans but differ from other populations of the same species in blood cell parameters. The lower number of erythrocyte and their relatively large surface area of our samples suggest a lower level of metabolism and relatively higher oxygen uptake. We suggest that this structure is probably not only due to adaptations to different geographic regions and altitude but also a combination of recent habitat reductions due to human actions and agricultural contaminants may account for the blood cell parameters as well as other genetic and morphologic patterns of these isolated and small populations of this species.