This study was undertaken to know the effect of fat diet (for eight weeks) on changes of inflammatory markers [tumor necrosis factor (TNF-${alpha}$) and prostaglandin $E_2$ ($PGE_2$)] and blood coagulation system [platelet aggregation function (PAF), prothrombin time (PT), activated partial thromboplastin time (aPTT)] in rats. Serum TNF-${alpha}$, $PGE_2$, biochemical markers, PAF, PT, aPTT, and body weight were measured and compared between the control (normal diet-rats) and the fat group (fat diet-rats). The weights in the fat group were higher than those of the control group. TNF-${alpha}$, $PGE_2$, glucose, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and creatinine levels were greater in the fat group compared with the control group. The degree of platelet aggregation was lower, whereas PT and aPTT levels were longer in the fat group than in the control group. These findings have shown that fat diet may cause inflammatory response, diabetes, liver and renal dysfunction, and disturbances of fibrinolysis and coagulation system.