This study aimed to evaluate the concentrations of α1-acid glycoprotein (AGP), haptoglobin (Hp), serum amyloid-A (SAA) and ceruloplasmin (Cp) in healthy and various diseased cats and establish reference intervals (RIs) for these acute phase proteins (APPs) in healthy cats. The animal material of the study consisted of 40 healthy cats and 152 cats with various diseases. The serum APPs in the diseased group were higher than those in the healthy group, and age affected Cp concentration in healthy cats. Also, the systemic inflammatory response syndrome (SIRS) positive (+) group had significantly higher AGP concentrations than the SIRS negative (-) group. In conclusion, this study contributes to the limited number of studies on RIs in serum APPs concentrations in healthy cats. The results of this study suggest that APPs are valuable diagnostic tools for identifying the inflammatory processes of various diseases, and AGP concentration could help determine the severity of the inflammatory condition.