Prothrombin time (PT) and the activated partial thromboplastin time (aPTT) are useful tools for the diagnosis and monitoring of coagulation disorders in Veterinary Medicine. Our objectives were: to establish reference intervals (RI) for PT and a PTT for the dog using the Start®4 (Stago), to compare the obtained RI with literature; to evaluate the effects of gender and age on the coagulation profile. Plasma samples of 122 healthy dogs (57 males; 65 females) aged between 4 months and 18 years, divided into three age groups (0-2 years old; 3-10 years old; > 10 years old) and grouped in to males and females were analysed. The RI were estimated following the ASVCP guidelines with the Reference Value Advisor software. The RI were: PT 6.7’’ to 10.8’’; aPTT 9.0’’ to 14.8’’. PT was significantly higher in females than in males. Dogs aged 10 years or older have significantly higher mean aPTT times than younger dogs. RI comparison showed a considerable percentage of cases outside the reference RI of the literature (PT - 79.3%; aPTT - 77.1%), demonstrating the need of each laboratory to calculate its own RI. The RI established in this study are applicable for the coagulation profile assessment in dogs.