The purpose of this study was to determine the diagnostic importance of coagulation parameters in cattle with natural theileriosis. Nine Holstein cross-breed cattle with theileriosis as infected group and 6 healthy Holstein cattle as control group were used in the present study. Mean fibrinogen level, thrombin time (TT), activated partial thromboplastin time (aPTT) and prothrombin time (PT) were not statistically different when control and infected groups compared, except for the D-dimer concentration. Quantitative D-dimer concentrations were determined by immune-turbidimetric assay. D-dimer values increased significantly (p<0.05) in infected group (631.55 +/- 74.41 mu g/L) compared to control group (370.00 +/- 59.94 mu g/L). D-dimer sensitivity and specificity were also determined at cut-off concentrations (372 mu g/L). Sensitivity and specificity of D-dimer values were determined to be 88.89% and 83.33%, respectively. D-dimer is thought to be important indicator in the evaluation of the prognosis in theileriosis cases. Analysis of D-dimer values before and after treatment in controlled case studies were suggested in future studies to enlighten the issue.