Since diarrhea is a significant problem in calves, the present study was undertaken to determine haptoglobin (Hp), Interleukin-1β (IL-1β), Interleukin-6 (IL-6) and Tumor Necrosis Factor–α (TNF-α) levels, which are known as inflammation mediators, in calves with diarrhea and healthy calves in order to identify the inflammatory condition caused by diarrhea. In the present study, 40 calves between 0-3 months of age were used. After clinical, systemic and haematological examinations, the calves were divided into two groups. Clinically diagnosed calves with diarrhea (n=20) composed the study group whereas healthy calves (n=20) were used as control group. As a result, the levels of Haptoglobin (Hp), Interleukin-1β (IL-1β), Interleukin-6 (IL-6) and Tumor Necrosis Factor–α (TNF-α) in the serum were statistically higher (P<0.001) in calves with diarrhea compared to the control group. Moreover, rectal body temperatures and the values of White blood cell (WBC), Hematocrit (Hct), Gamma glutamyltransferase (GGT) were also determined high in calves with diarrhea. Interms of Red blood cell (RBC), Hemoglobin (HB), Alanine aminotransferase (ALT), Aspartate aminotransferase (AST), Total Protein (TP) and Albumin (ALB) concentrations, no statistical difference were found between the two groups.