© 2016, © The Author(s) 2016. Objectives: The aim of this study was to characterise the response of acute phase proteins (APPs) in cats seropositive for Dirofilaria immitis and to its endosymbiont bacterium Wolbachia. Methods: The APPs serum amyloid A (SAA), haptoglobin (Hp) and ceruloplasmin (Cp) were measured in 25 seropositive cats and in 16 healthy seronegative cats. Results: SAA and Cp concentrations were significantly higher in animals with D immitis seropositivity that exhibited clinical signs related to the disease, and Hp was elevated in all D immitis-seropositive animals. There was no significant correlation between APPs and D immitis or Wolbachia species antibody titres. Conclusions and relevance: An association between feline seropositivity to D immitis and APP response was demonstrated. Increases in serum SAA and Cp concentrations were related to D immitis-associated clinical signs, whereas Hp increased in all seropositive animals.