In the context of a small animal veterinary clinic in Maceió, Alagoas (Brazil), it is observed that most cases of intoxication result from contact with pesticides or improper ingestion of medications. In a remarkable episode in 2017, we treated a 13-year-old female Cane Corso dog presenting severe symptoms of intoxication. Electrocardiographic analysis was crucial in identifying the cause of the symptoms, which was suspected to be poisoning by Rhinella marina, also known as Bufo marinus, or locally as the Cururu frog. Confirmation of the diagnosis came days later, with the discovery of a Rhinella marina carcass near the animal's living area. Bufotoxin, the main component of the venom, had a significant impact on the dog's cardiac receptors, altering the electrocardiogram and inducing a sinus rhythm with ventricular fascicular tachycardia for an extended period. Such toxins, including bufadienolides and bufotoxins, act similarly to digitalis, blocking the sodium and potassium pump of cardiac cells. Rhinella marina, an amphibian native to Central and South America, belongs to a genus with hundreds of species and is widely distributed throughout Brazil. Although there is no national statistical data on its occurrence, zootoxins, including toad venom, are responsible for 2.4% of animal intoxications in Italy. Treatment consisted of fluid therapy and intravenous administration of lidocaine to normalize the heart rhythm. After three days of hospitalization with intensive treatment, the dog was discharged with a normalized electrocardiogram.