An investigation was carried out to assess and compare the seasonal changes in haernatological parameters of rudd (Scardinius erythrophthalmus) parasitised and unparasitised with Cryptobia tincae. Prevalence was 56.19% in winter, 35.71% in spring, 23.53% in summer and 23.63% in autumn. No statistically significant differences were observed in erythrocyte, leucocyte and haernotocrit values between infected and uninfected rudd for any season (p > 0.05). Significant differences in seasonality were only found for erythrocyte counts (p < 0.05) in the parasitised and unparasitised rudd. In the leucocyte profiles, significant differences were seen only for lymphocytes in autumn between parasitised and unparasitised fish. While the seasonal differences (p < 0.05) were determined for neutrophils and eosinophils in the parasitised rudd, the differences were estimated only for eosinophils in the unparasitised rudd.