Objective. The present study was conducted to measure D-dimer concentrations and assess their value in disease activity in dogs with giardiasis. Furthermore another purpose was to analyze correlation between cyst excretion and D-dimer levels to those of dogs naturally infected with Giardia sp. Materials and methods. D-dimer analysis were performed in three groups of dogs; (i) 15 dogs with giardiasis to those of treated with secnidazol, (ii) 10 dogs with giardiasis, left untreated as control group, then were compared to those of (iii) 17dogs without giardiasis, used to detect reference ranges for D-dimer values as control group. was a correlation between D-dimer levels and logarythmic cyst counts. Results. The D-dimer range in healthy dogs was <0.1 mg/L. In dogs with giardiasis, the D-dimer concentrations were greater than those of healthy dogs (p<0.05) and (p<0.01), respectively. The mean initial plasma D-dimer level was 2.84±0.50 and 2.99±0.61 ng/L in treated and untreated control groups. At the final follow-up evaluation on day 10 was 0.27±0.50 and 2.14±0.61 ng/L, in treated and untreated control groups, respectively, which was significantly lower in treated group (p<0.001). The area under curve (AUC) of the receiver operating characteristics for d-dimer was 0.922 (z-value = 12.977, p<0.0001). (95%CI: 0.780-0.885). At a cutoff value of 0.1 ng/L, the D-dimer measurement had a sensitivity of 87.2%, a specificity of 90.9%. Conclusions. As a result D-dimer concentrations measured in giardiasis support the probable link between probable pro-thrombotic and inflammatory condition.