The objective of the present study was to validate the use of blood collected from an indwelling arterial catheter for analysis of haematological, coagulation and inflammatory parameters in canines compared to venous blood collected directly from the jugular vein. Blood samples were collected from 11 dogs. Agreement between sampling methods was found for neutrophil and monocyte counts, prothrombin time, activated partial thromboplastin time, antithrombin, protein C, factor VIII and C-reactive protein, whereas a statistically significant difference was found for white blood cells, lymphocyte, erythrocyte and platelet counts, haemoglobin, haematocrit, fibrinogen and thrombin time (TT). In conclusion, it is necessary to be aware that results from a complete blood count obtained from canine venous and arterial blood samples may not be comparable. Values for haemostatic parameters from arterial and venous blood samples, with the exception of fibrinogen and TT, were however statistically identical.