Hyperfibrinolysis is a risk factor for bleeding; compared with humans, dogs have accelerated fibrinolysis. Antifibrinolytic drugs have been used in veterinary medicine to reduce postoperative hemorrhage in greyhound dogs, a breed at greater risk for postoperative bleeding complications. In humans, tranexamic acid (TEA) and ε-aminocaproic acid (EACA) are used to inhibit fibrinolysis. This study sought to determine the minimum plasma concentrations of TEA and EACA needed to completely inhibit fibrinolysis in canine blood after induction of in vitro hyperfibrinolysis. The concentration of EACA and TEA needed to inhibit fibrinolysis was 511.7 µg/mL and 144.7 µg/mL, respectively. This study confirmed that dogs were hyperfibrinolytic compared with humans, who require EACA and TEA concentrations of 122 µg/mL and 14.7 µg/mL, respectively, for complete inhibition of fibrinolysis.